Ok you can disagree with me all you want but it makes me so fucking uncomfortable when a m...

That annoys me so much you have no idea! I hate it so much when a mangaka decides to do that, and unless the rest of the manga is good that usually ruins it for me. That's one of my very few problems with Love Mode (I still love the hell out of it) and it's one of the reasons I decided to drop this. ╥﹏╥ It's just not my personal taste, but it's not the same for everyone. So for anyone who enjoys this, I'm glad. ヾ(❀╹◡╹)ﾉ~

I actually like the way this story's heading... people are complex and come with baggage, and I like to see that explored. I'm sure the main couple will have their happy ending when it's all said and done anyway. :)

Haha
I get what you mean, but at the same time I think it makes it more realistic. On real life we also don't feel comfortable thinking about your boyfriend ex, but as we all know life is a jerk and someday you'll have to deal with it.
So, I'm a fan of past lovers. Makes things more complicated and bittersweet :)

It honestly comes down to personal preference, some people like it, others don’t. I love me some complicated characters but I don’t like it when the mangaka shows the past relationship with a lot of details. However, to me, it also depends on the story of the manga, where and how it’s presented. Here are some examples of what I mean (personal opinion, feel free to disagree (●'◡'●)ﾉ and also all of these are my favorites so I don’t hate them at all):

http://www.mangago.zone/read-manga/loveholic/
See this one is the case that I loved the flashback with the ex-lover. It’s shown at the end of the first volume, after we have the seme and the uke interact and develop their relationship. The flashback breaks your freaking heart, and then the second volume resumes with the current relationship. However, now the reader has a better understanding of what the seme went through and you know the reason for some of his actions.

http://www.mangago.zone/read-manga/love_mode/
What bothered me more about the flashback of this manga isn’t so much the flashback itself but where it is in the story. It’s the last arc, so the last impression the reader gets is Aoe and Shiki, sure there’s a little scene at the end with Izumi and Naoya where Shiki entrusts Takamiya and Aoe to them, but I personally don’t care for it. I would’ve loved the flashback arc in between the mess with Naoya’s family, when Aoe is alone. That to me would’ve been a more appropriate moment to hit the readers with the feels in my opinion. This one is still one of my all-time favorites and an excellent manga.

http://www.mangago.zone/read-manga/punch_up/
For this one I don’t have a fancy reason for hating it, it’s a super shallow and an unjustified reason that I will not defend so I won’t mind if anyone calls me out on it. I loathe Yuya so I don’t want to see him with Kouta and I always skip that chapter when I re-read it. Childish and stupid, yes, but what can I say, even I have my moments of pigheadedness. It happens.

For this manga in particular I just didn’t like that the lover relationship wasn’t developed at all (in my opinion) before the mangaka decided to jump into flashback mode. I would’ve loved more of Mako and Kouta’s relationship struggle before jumping to the ex. Plus, the story just wasn’t super engaging to me, though I love the art style. Again this is just my opinion, the story isn’t bad at all, it just didn’t appeal to me personally.

Sorry for the long, rambling post and again, this is just my opinion and everyone is free to disagree with me, that’s totally fine. The important thing is that we enjoy ourselves reading the things that appeal to us. ヾ(❀╹◡╹)ﾉ~

I would agree that it ultimately comes down to how good the mangaka's storytelling is! If it's done well, then it's done well. If it's underdeveloped or feels cheap, then I'm not a fan either.

I don't mind past lovers flashback but man....I too hated the Punch Up flashback because I hated Yuya as well! It's ok. It's not childish at all.... I feel you!

All i can say is, you can't do anything about the past.

I don't mind exes in manga in general, they make a good source of jealousy, but side chapters like this get a bit uninteresting since I can't make myself cheer for them when I know they'll break up... I prefer it when the ex find a new partner and their own happy ending instead :)

In the end it all comes down to your personal preferences: some like innocent, blushy uke, some don't; some like shota, some can't stand it. In this case, some people find past partners an interesting plot device and like the realistic, complex aspects they bring, but personally I'm not good at dealing with jealousy haha. I tend to avoid any complications or entanglements when it comes to love, you see? I want it to be neat, like when you break up with someone, you're done, no more connection. You don't ever come into their life again and they yours. I mean, I'm totally cool with a character sleeping around before they enter a serious relationship (again, some people can't stand this), but past partner, especially someone the seme/uke had something aside from/more than sex with, showing up is a no-no. It's too emotional for me. I can see that the guy and Mako-san had /something/ together, not just simply fucking.
It's just like in real life. I'm fine with the fact that my boyfriend had loved other people in the past, but /actually/ seeing how happy and lovey dovey he was with his ex when they were still together is a whole different matter for me.

It bothers me a bit too, especially after the main couple has been established. I know authors like to throw in a flashback once in a while to flesh in a character's past and to add a little something, but I personally could do without. The main story is here and now, and I don't care about past lovers. It bothers me the most when the flashback is toward the end - for me, it interrupts the mood (my personal feelings) of the main couple.