It's not the big brother's attention that Keita wants. He saw Mitsu as his friend and so he's upset about his brother stealing him. So he's stealing Mitsu's attention whenever he can which in turn is cockblocking them.
http://www.mangago.zone/read-manga/smell_fetish/mf/c001/38/
And pages 12-15: http://www.mangago.zone/read-manga/smell_fetish/mf/c002/
Have you ever met a child before? Niece, Nephew, Sister, Brother.. Etc... They are attention grabbers, they want everything for themselves, if you don't pay attention to them they will get mad. Their not intentionally thinking "Of their dating so let me cock block them".. All their thinking is "I want this person attention, pay attention to me"... Children are not mature enough to understand that "these people are dating so they want privacy, i shouldn't interfere."... But also look at the situation their in, the mom is not there, the father isn't there, the only person is the brother and the boyfriend. When their together of course he is going to want to play, their a bundle of energy that cant be controlled by just watching TV. What do you expect? Keita watching Tv like a good boy while the couples fuck like bunnies is their room?.
Keita is a cockblocking little shit
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