The first (3 chapters) story is really sweet. I always find it interesting when there is a significant age gap and the older man ends up being an aggressive uke, which seems to be more common the more I read. Skip the third story (chapter 5); it's worthless. The last one is also really kindhearted and pure. Seeing them fuck would be hilarious with how naive the one guy is.
Boku no Shiru Anata no Hanashi