Responses
I just assumed so following Doyhe's comment http://www.mangago.zone/read-manga/an_innocent_sin/mf/m_chapter-69/pg-8/ When he says "I wanted to do it with you". And in chapter 69 Nayeon realised Doyhe was the first relationship he mentioned in chapter 57. Plus Noah says in chapter 57, "no we didn't do it" when she asked if they had sex.
YYEEAA ITS BACKK....! and i wonder if this dude and Noah had a thing going on in the past.