
Ah now I get it why it's called aioi musubi. I remember watching an anime, forgot the name, but there's an old lady there explaining about musubi. Musubi generally means knotting but in Japanese it can also be translated as the connections between people and also the flow of time. It's like the nature of a knot itself, they converge and then they take shape. It twist, tangle, sometimes unravel, break, and then connect again. This put another light into the manga. And sensei did a really good job doing it.

thank you for this informational bit; my own language only got one (comparable) word for that state, with about 16 equivalents in english. But none of them is positive or at least neutral in meaning, so it's fascinating to learn that japanese has a word to describe "the object, the state, the process" without stating at the same time "it's like this, but no good"
Honestly the plot is tangled in some places and chopped up in others, but I think this is what the author actually wanted to say:
So, all those years the uke was emotionally dependent on the seme to the point it turned into a complex which reached it's highest point after the death of his father.
The uke was completely emotionally unavailable because his relationship with the seme was a surrogate for a relationship relationship, which made his partners and anybody who was interested in him think he already had his heart set on someone.
He want out to bars and sought sex partners because, well he likes sex and wants it. That's all there is to it.
The seme realized his feelings for the uke after experiencing jealousy.
They started dating, with the uke completely aware he wasn't in love with the seme just incapable of living without him.
After the seme had a little makeover which gave him a mature look, the uke finally saw the seme wasn't just the boy whose presence he was addicted to, but an actual member of society, and as such a potential mate.
The uke started noticing the seme, and fell in love. That completely twisted him up cause he didn't know how to act.
Their feelings are mutual and happiness.
As for the ex sex friend, he wasn't interested at first, but with time came to like the uke, even though he knew the uke would never see him as something more.
The business owner saw the uke as a kind of replacement for the uke's father, while the uke only saw him as a close friend and a reminder of by gone days.