Considering the show points out that he was being tested by his future self to see how strong their bond of love with, not Chibiusa shouldn't have disappeared. He sees these visions that say "bad things will happen to Usagi if you continue to be with her", he thought he was doing what was best for Usagi not himself so I think he was justified, putting her well-being before his relationship with her is selfless of him, that is at least how the show wants you to see it. Stars was different, they didn't "break up" in the same sense, Mamoru was kidnapped and apparently the timeline changed to one where he would remain that way.

Mamoru has spent the entire 'romance' between he and Usagi basically out of his mind. First, he's Tuxedo Mask - who only existed during periods where Mamoru blacked out and/or thought he was dreaming! Good for cultivating an emotional attachment between he and Sailor Moon, not so good for bringing that into the real world. Then he was Endymion, and got dumped with the full weight of Endymion and Serenity's romance just before he was brainwashed into Dark Endymion. Dark Endymion had his own moments with Usagi... but is anyone but Usagi really inclined to count that? The Moonlight Knight wasn't exactly Mamoru, Japanese college student, either.

Now Mamoru's kid who has found himself in the line for some sort of destined romance. He has all of his memories (in-so-far as Endymion, Tuxedo Mask, and the Moonlight Knight go), he has the emotional attachment to the girl, the drive to protect her... and finally his obligations to society, and himself. He is a nineteen year old (!) dating a fourteen year old girl seriously. The various tangles associated with this are enough to make him want to take a step back and process, disregarding all the magical aspects of their lives.

He doesn't take a step back. Instead he goes full speed ahead into their relationship, despite whatever reservations he has. He ignores them because he loves Usagi, he likes Usagi, and he finally feels like he's complete - a product of returned memories, a sense of identity, and Usagi herself.

And then Chibi-Usa shows up, and the dreams start.

Mamoru spent the whole first season either ignoring or being driven by his dreams of a Princess, and then it turned out they were real. Doing the sensible thing and ignoring them is completely insane to Mamoru, now - look at what happened last time! But at the same time, he doesn't want to have to give up Usagi, just when he's getting his feet under him again.

So Mamoru has to separate from Usagi or Bad Things Will Happen.

Here's where Mamoru makes his, 'I'm a dumb kid,' mistake. He doesn't discuss things with Usagi, because he knew that she might be able to talk him out of it. NOOO, instead Mamoru has to find a way to make a clean break. So he draws on every reservations he had ever had about their romance and breaks up with her - he tells her she's too young (I'm too old for her), she's too clumsy (...well, she IS), and she's too weak (he's not strong enough to protect her). He uses every self-justification in the book, because he DOESN'T feel that he's doing the right thing.

But Mamoru still can't help going to rescue her - which wouldn't exactly be an issue if he could maintain a bit of professionalism about it. "I'm here to help because the WORLD MIGHT END, it has NOTHING TO DO WITH YOU." Instead he and Usagi repeatedly clash. He sends out mixed signals about his intentions. He goes for her first, and doesn't show quite the same consideration for the other girls. He doesn't intend to hurt her - beyond making trying to make her see that he's not going to be with her.

Chibi-Usa doesn't disappear because her particular future wasn't negated - Usagi always had the chance to convince Mamoru that they could face the future together (and, forewarned is forearmed), and Mamoru was always on the verge of losing his resolve. Hurting Usagi hurt him just as much, if not more.

What he did to Usagi while he was trying to break up with her wasn't right - he was deliberately trying to hurt her on several occasions so that she would give him up for a lost cause. But it WAS justified, because he was convinced that breaking up could somehow save her from a terrible fate. He was always trying to do the best thing for her - which was the stupid part (on his part). During R, he wasn't treating Usagi like an equal at this point. He refused to talk things through with her because he didn't have faith in her ability to reason (she would think he was wrong... but what if he had talked to her, and she hadn't!) or his own rationalizations (...justified, because he spent the last several months completely out of his mind. If the dreams were heralding a new era of crazy!Mamoru, it was still better to have Usagi out of there).

This is all IMHO. Loooong, and not particularly well-thought out, just typed very quickly.

I read on Tumblr someone going all like "oh, ditch the break-up act in the anime, i want the manga where they were supposed to be having sex".

but, who's to say they didn't do it when they got back together? and he's older in the anime than in the manga.

but that's not the point here

I also find his actions justified and that served to make their relationship stronger. after that break-up, they would get past anything because they are endgame.

Everyone else has said pretty much everything really. But yeah, I believe Mamoru was absolutely justified in doing what he had to. Quite honestly, I think he's actually more responsible than Usagi because he's considering the long-term goals rather than short-term.
Ie; Mamoru thinks breaking up with her means she'll have some kind of future without him. Vs. Usagi's 'I want to be with you -nooow- '.

Which, realistically speaking- he's actually right and has the right reasons for it. I mean, he spends a good portion of the break up hurting every bit if not more than Usagi over the relationship. Considering he doesn't have many positive and emotional attachments in general, this is a big deal.

Also, shall it be added he doesn't actually have anyone to talk to about this that's impartial considering everyone that knows about their lives- are all her friends and guardians. So him internalizing this makes perfect sense.

Eh, honestly I don't think I have more input I supposed. I just believe he's justified in his decision and actions.

I also think Mamoru's actions were justified even though he was very cruel to Usagi but he was doing the right thing. I know a lot of Fans might hate Mamoru for behaving like that but we have to think about it what other solution was there, it was the only way he could been to save her. We know from the inside it was killing him because one thing he hated was to make Usagi cry.

Many Fans judge him very wrong I'm pretty sure if they were in his place they would do the same, I know my love one would hate me but I would do anything to save his life because without him I couldn't live. I believe that's how Mamoru felt Usagi is his life, his shining star

NerdyPanda wrote:

For me...I'm just having a hard time understanding it because he knows what happened in the past and he should know they are destined to be together int he future [and in the present] so....why hurt her!?

Mamoru doesn't know they are destined to be together in future. He can't know that.

Nerdy Panda wrote:

He also just kind of plays her along by saving her every time in battle. I know he probably thinks that this is the "best" thing but...why make the effort in saving her every time? He is just kind of putting the happiness of being together in front of her and just pulling it...every....time.

On one hand it's kinda sending her mixed signals. On the other hand - would remaining out it be really right? He tried to in dream episode and it could be fatal for Usagi.

Nerdy Panda wrote:

It's so painful to see little Usagi so upset over this.

Yes, it is. But he suffered too...

I know his actions were justified, but to me that was the stupidest way to test the bonds of their past relationship. It was as if King Endymion was playing a harsh joke on his past self and Usagi. For me, it's clear that the test was to go through Hell to come back stronger, but I felt it really ruined the true beauty of their relationship. The first season had them come together at the end, then in the beginning of the second season they forgot each other, and then when he remembers, they break up. Season 3 and 4 barely touched on their relationship, then he dies in Stars and returns at the end. What the hell, man?

bump

They were-or should I say would have been if it weren't for the all "doomed lovers in a past life forced to defeat the evil that destroyed them" bit. I mean come on, they needed the crystal, they found the crystal, they fought for the piece of the planet so the past didn't repeat itself and doom the planet, died, resurrected and regained their memories. Plus, even when they DIDN'T have their memories, they still found themselves protecting each other out of pure instinct.

Also they kinda sorta met their future selves and their kid.

if it were any other show with different plot elements, I would have said yes. But in the world of sailor moon, it was seriously unnecessary and could have been handled in another way.

I definitely agree that it was completely unnecessary. He should have realized that they are stronger together than they are apart. At least his manga counterpart realizes that.

Yeah, having just rewatched R recently, I agree that it just comes across pointless. We spend all of Classic waiting for them together, but the instant he does he gets brainwashed and turned evil. Becomes a good guy again only to lose his memories, and then gets his memories back only to break-up with her. It was just so tiresome. Part of the reason why I think the Black Moon arc is when the original anime starts to wear itself out, but I disgress.

It may have been better, had all the stuff previously said above not happened prior, or if Usagi and Mamoru had more beathing room for their new relationship that lasted longer than one episode. I am not entirely against the idea of a break-up arc, since a little drama can go along way. But this was just done poorly. Poor reasoning, poor timing, poor execution, and poor conclusion. I can really watch the Black Moon part of R only by skipping over the break-up stuff because it is really tiring.