Hair clip guy is Shigeru (I misspelled his name eriler and yes he is the guy that chose to sell gyoza with Louis and Yuuichi) and Masa and his story (the start of their relationship) is here http://www.mangago.me/read-manga/kare_to_kare_no_ijiwaru_na_kyori/sa/sa-c001/3/ I hope this answers your question. Although I do apologise because, I realised after writing my comment that the timeline, of the spinoff and the current chapter of the original manga, may differ. But I am still annoyed at Masa because he knows that Tatsuya (uke? main guy) likes Daichi (seme? celebrity/actor) and they are practically dating, yet Masa is still after him?! Anyway it's just my opinion. ╮( ̄▽ ̄)╭
The butting into the relationship, that I can agree a bit but the timeline between the two stories probably is different. Masa is not perfect but I don't like now that readers think of him as a 'cheater' or player of Shige's feelings. Heck, two of my hardcore fujoshi friends decided to no longer read the spin-off, which in my opinion is far greater than this here.
I am pretty annoyed at Masa because he is still going after Tatsuya even though, at this point, he already knows that Shinge has feelings for him and has done stuff with him. Masa should just leave Daichi and Tatsuya alone and work on his own relationship instead of butting into theirs. ( ̄ε(# ̄)Σ On a side note Louis and Yuuichi are just adorable and sweet.