Yasuda is 32 years old

Ryousuke’s nearing 30

Sakura is 30

Hisato is a 300 year old vampire

Taesung Park is 29 years old, one year shy of 30, so he can slip onto this list. Plus he looks older than his age.

Leo is 63

Masaki Tsuji's a 30-something year old high school teacher

Dojun is 37 years old

Soushi is nearing his 40s

Jaeha is 32 years old by the end of this manhwa

Yuki Miyamura is 30

Kazushi is 30

Seiji Tajima is forty-something

Suha is 32 and Jiwoon is between 29 - 30 years old, because in chapter 15, it's mentioned that he is younger than Suha.

Both are in their 50s

Ifukube Yamato is 30 years old

Jung Jaehan, the handsome chaebol is 32-33 years old while  movie director, Yoon Heegyeom, is 34-35 years old

Odu is 30 years old

Nouchi Hisanori is 38 years old

Nozue is 39 years old

Yoake Itaru is 38 years old

Teruaki Hoshi is 33

Kazama Shou is 31 years old. He looks much younger than his age.

Tomoya is 30 years old

Satoshi Nekota is 35 years old

Imagi is 32 years old

Imagi is 32 years old

Seiji Shinonome is 31 years old

Writer in his 30s.

Yohan is 31 years old

Reiji from Number One no Baka Inu Choukyou is 30 years old

Harasen is a single, lonely 37 years old high school teacher

Yuuki Ritsu, is 29 but gets a pass onto this list

Paul Auster is 30