Another (seperate) plot development that I predict;
Ogura eventually tells fiancee about her fetish [or he finds out some other way], he's cool with it, he tries to do it with her, but she just can't enjoy it unless it's Shuuma. I feel like they've been hinting at something like that from the beginning, with Shuuma's inner monologue in the first chapter about "I want to make her unable to attain pleasure without me.", and Ogura's comment in Chapter 19 about how "It just has to be Aguri-kun to tickle me". Idk if it's the same in the original Japanese, tho. Sorry for the run-on sentence.