Honestly, I've been looking for realistic slow-paced development romance stories for the longest time where you can SEE the transition, and I'm so pleased I've found it here. It's difficult to find that sort of thing in manga, especially in the genre of BL, but there's so much care put into the dynamic that I can't help but love it. The story is dealt with such a mature way, and reads like a casual story that might (?) happen. The problems that rear up to challenge their relationship are realistic ones--and it's not tropey at all; or at least if it is, it's done in such a very great way.
I also love Sakurai's personality: Sakurai's adult way of looking at things is such a good change and a breath of air from regular age-difference relationships--it's not just about age; it's about how you treat a situation or react to one. Youichi too is stellar; he's not held as this ideal "other person" to get, and he struggles in his own way with personal demons, and with the relationship that Youichi does.
EDIT: I realize someone below mentioned they found Sakurai boring, but I actually really liked him! If anything, it was more or less Youichi who I was more 8/ about until we learned more about him, and the manga changed into his POV.
I love also that the story doesn't focus primarily on their relationship (as in, it's not the only thing). Sakurai has his work, Youichi has his school--and the story also brings in a breath of fresh air of the dynamics of the secondary characters (which is so good honestly, Shouta's relationship with his father, Youichi's two caretakers worrying about him, etc). It's so well done.
This is such a great manga? You literally couldn't replace these characters with anyone except themselves and still get the same story. Love it, love it, love it. Just not sure how I feel about the jump from the second last chapter to the epilogue chapter:
felt like it wrapped things up a bit too fast from having sex (lol) to a point that was unimportant about Youichi's mother--but it was good to see confirmation about that.