SPOILER!!!!!!!
I will just refer them as seme uke (I forgot their name)
The reason why the semes action is like that is because since they were a kid the seme is already I love with the uke, however the uke being a kid did something that made the seme feel disgusted by himself, the uke regret it and and wants the seme to be back in his life but the seme feeling heartbroken but still love the uke, so what he's doing is push and pull bcs when the seme (he thinksthis okay) i am not at good in English im sorry) treated the uke good he was betrayed at the end.
The uke almost died right? Well he was actually given a second chance, from the semes mother, you can see at the early chapter that semes mother died, however since her soul is still alive and well and saw that if the uke will die without reconnect with the seme ( her son) the seme will be more heartbroken, since her mother cannot fully resurrect the uke she just gave her a pills that will help him to not turn as a bubble, he didn't know (the uke) that the semes mother help him.
So they will able to reconcile their relationship however his pills is already empty do if feels a sad or something emotions he will vanish
Unfortunately the uke vanish bcs there's something that make his emotions trigger, however his pills were already empty bcs while he was busy doing everything to get the semes attention his emotions is unstable, bcs the seme is also uptight
The seme saw that the uke was disappearing he hugged the him but it was already too late, he also found out that the pills ukes was taking is not a ordinary pills, the seme was heartbroken and was about to follow the uke but he was stopped by his sister and did some talking that if he will do this the uke will not be happy, so he continue living but his eyes are not,
When he dies of old age he smiled knowing that the uke is waiting for him and they are also given a second chance so it's a happy ending..