Shojo to Nokemono

What will become of the romance between a 30-something girl with no experience with men and a wild, popular guy? Miki is a dull girl with no experience with men, but secretly admires Kajio, who is popular in the company. A worried colleague introduces her to Nagi, a wild-like boy who is rumored to have slept with a thousand men. The two live in completely different worlds, but for some reason Nagi begins to take an interest in Miori...?!

(Source: Akita Shoten, translated)