Tsubami is literally just a tsundere with extra tsun. It's a nice break between the intense sexual abuse in the other chapters, even if it's hot. It reads half like porn and half like psychological horror sometimes, so seeing this romance subplot is like getting a bit of rest before diving back into this man's shitshow of a life.
Honestly it seems merged into the author's self-description. No wonder Ueno's a complete void of a character, as a self-insert the author doesn't really need to work on character background or motivations.
This manga is making me feel sad.
Man is literally getting sexually assaulted. Also his dick didnt look small when he was getting a handy from Tomoki(or whatever her name is) and it's big enough to bulge his pants. Let me tell yall, if its bulging like that through he pants, then he is in no way "smalldicked"
The small part seems wrong, of course it could be compared to other males in this manga universe, in the normal world he would be average or even above, it was clearly the author wanting to make him as miserable as possible.