why, why, why can't there be at least one step-sibling story where the characters grow close, but not romantically or sexually? why is there no distinction between the many different kinds of love and even physical intimacy that are possible, and lust (ok, this hasn't reached that point yet, but it seems the mc more or less gave up and agreed it will eventually)?
it's a bit sad this is going straight for the cliche step-siblings romance route after the great start where they defied (or at least delayed) that expectation so well. would've been good if they agreed and at least tried - or even succeeded - to keep a "brotherly" relationship with each other, and little by little overcome the anxiety of the gender difference and other obstacles, until the "final boss" obstacle - seeing each other romantically involved with 3rd parties. suddenly reverting to a "someday marry me" plus just keeping up normal sibling appearances for the parent's sake plot was surprising, and a bit disappointing.
also akira's character being so aggressive at home really doesn't match well with her usual anxiety... i know her change, somewhat forced by the brother, was a big point of the earlier chapters, but this end result's still too sudden. like, right after the bathroom incident she was forcing herself to act like that and enjoying the revenge of seeing him feel the awkwardness that he unknowingly made her feel before. but now she doesn't even seem like she's acting or forcing herself, she's just like a completely different person.
Try Gimai Seikatsu
it's a more realistic approach (though it still deals with step siblings falling in love)