Before dying black uke (xD) send main uke his belongings and there was his diary. But uke didn't read it and he throw it away. Later on seme was asking him if perhaps he didn't get the diary, but he lied that he never saw it. And since seme is super sketchy and keeps on lying it seems like there could be a clue inside the diary why black uke died.
About 29: main uke is 28, seme first fiance and black uke died at 29 xD
He didn't throw it he kept him with him in his apartment seme found it one time and burnt those letters friend wrote and everything uke never gets to know anything, uke is not bad his life was enough struggling due to his father and career related issues and fuckin around too that he never look back at those letters. And forgot about them later on

1. If he only read the diary, I'm so mad.
2. Is uke gonna die once he turns 29? XDDD