I feel .... Ginga ... probably did stuff with Kouetsu thus ... the theory the doctor said ...

You're not wrong...if you go back a ways in the comments to 97 or so there is a doujin told in the perspective of Ginga, the user Kimuchi explains it


Spoiler if you want to know
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"it's a doujinshi of this manga by the same author lol. i just read it & it seems that both kouetsu & ginga have been in love with yuuzen since childhood (but the story is told through ginga's perspective). they both felt heartbroken that yuuzen slept with a woman, so they had sex at the exact same hotel room that yuuzen did, & there started kouetsu & ginga's sexual relationship. it first started as a fling to blow off some steam as well as "forget" about ginga's love for yuuzen, but it escalated to the point where he somehow needs to have sex with kouetsu to suppress his urges for yuuzen. on the last page, ginga is aching for yuuzen's love (even though yuuzen only sees him as a friend) & says that he's about to break, but kouetsu says it's better if he did bc that makes him even more alluring. so you can imagine how ecstatic both of them were when they found out that yuuzen is actually an omega lol. sorry about that (▰˘◡˘▰)"

Oh my god. Thank you so much for the spoiler now it all make sense ...