Ooh let's see! My old answers to a similar question still apply, and I haven't read fics in a long time, but if I were to list some more, hmhmhm...

Take Me Home is one I really like. REALLY like. Reigen sleeps most of it. It has Ojisan×Mob oral!! And delicious mutual reimob with a very desperate, hopeful Mob touching his shishou while he sleeps♡ Really made me want reimob where Reigen's cock slips out while they're kissing too much and they gently but hastily put it back in...

A Different Kind of Lesson is a ton of joy! Mob with a high libido is fun to see, and he's also very adamantly anti-condom (lmao). A very blunt Mob is good to have now and then.
Awkward Firsts, Seconds Next is so cute too...Reigen's impatience killing him while Mob keeps being nervous and drawing back is so clumsy and cute...*Mob jerking Reigen off to cum inside him...*begging the other to hang in there so they can cum together...gripping my head I think I hauve covid

kisses for beginners is cute!! I love when text in Reigen's POV is messier and quicker than normal, like his talking style! I want to think about reimob first kisses more...
//Self-harm> Come Out of Your Shell is a rarer one for me, since I don't really vibe with self-harm, but I like hurt/comfort. Mob's growing shock and upset at them existing, and the following, desperate little wound kissing to make it better is sweet.