Twin Star Exorcists‘ Rokuro Enmado is your typical battle shounen protagonist: hot blooded and stupid with at first glance nothing good about him, which doesn’t stop him confessing to semi-strangers regularly only to be shot down just as regularly. Only his crazy shark like teeth set him apart from dozens of other bland, brown haired protagonists with tragic pasts. Because of course that’s the reason for his current uselessness: a deep seated trauma, something that happened two years ago and which he hasn’t been able to process. He used to be a hugely powerful exorcist until this happened but now refuses to have anything to do with it.
Otomi Mayura is his childhood friend. Beautiful, smart and outgoing, she seems everything Rokuro isn’t, so why does she hang around him so much? Because of course being a childhood friend, she both feels a bit responsible for him and loves him. She knows something about his trauma as well as his real character, which is why she sticks by him and tries to somewhat take care of him, though this last isn’t as pronounced as with some childhood friends. More than anything else she wants to keep Rokuro safe and for him to love her as much as she does him.
But Otomi is doomed to fail in getting Rokuro to love her because of this girl, Benio Adashino, superstar exorcist, completely devoted to her quest and almost emotionless outside it. She and Rokuro don’t quite hit it off, she seeing him as a slacker, he seeing her as the naive fool he was before his trauma, but of course this is only temporary. As much as they at first dislike each other, there’s also a mutual attraction as each starts to recognise the other’s virtues. Specifically, it’s Rokuro’s willingness to protect and fight for her that appeals to Benio, not so much his actual personality. Again, typical battle shounen behaviour.
Twin Star Exorcists is rather generic in its characterisation and plot, if well executed, and it’s this genericness that makes it easier to spot the problems with how its depiction of romance it has in common with many other battle shounen manga. Romance in these series is a matter of grand gestures, extravagant promises made by the male protagonist to the heroine, often as it is here, done before he knows anything about her. She meanwhile falls in love almost against her will, despite her initial impressions of him being less than favourable. Indeed, often the male lead remains a loser in everyday life, no matter how many demons or impurities he slays. He may not realise that she has fallen in love, but continues treating her (and everybody else in a skirt if it’s a battle harem series) the same as before; she certainly won’t tell him until she’s absolutely sure of him and her feelings both.
The poor old childhood friend meanwhile has seen the boy she loves confess to every girl he ever met, save her, while she stood there on the sidelines patching up his ego after the inevitable rejection, taking care of his domestic needs or helping him cope with his dark and troubled past. Either she lacks the courage to confess because she’s afraid of rejection, or the stupid fucker she loves is too dense to realise why she’s so friendly and kind. Superficially the childhood friend looks like a gender flipped Nice Guy, but in the end it’s still a very blokey fantasy to have a beautiful girl fuzz over you and do all the domestic chores for you without you having to invest anything in the relationship. No emotional labour necessary and you can’t fool me into thinking those dense protagonists don’t think of the childhood friend as the emergency backup girlfriend candidate.
The main heroine of course doesn’t have to engage in all that emotional labour. She’s free to be aloof or antagonistic, bad at household work, a dangerous cook, as long as she’s beautiful and almost but not quite as good as the protagonist at the demon slaying. She’s the unobtainable ideal up until the point that our hero either surpasses her through his innate talent at whatever magic thingy she needed years to train for (said innate talent manifesting itself mainly through LOTS OF SHOUTING) or because he’s the first man who wanted to protect her and sees her as a real girl. Because boy, gender roles are not very enlightened in manga/anime Japan and no matter how badass she is, secretly she wants to be a proper girly girl. Again though, the point is that our hero doesn’t have to invest all that much in the relationship; none of the tedious work required that a real relationship would entail
And all of that is perfectly acceptable in fiction, if it wasn’t so omnipresent in manga and anime stories (and to be fair, in a lot of western media too). If almost every story you read says it’s alright to not make an effort to be attractive and you can still get all the girls even if you’re a loser and a slob, just as long as you make the right noises about wanting to protect them, that’s not going to do wonders for your interactions with real women.