I think he did because they said he was drunk and then hung himself. They showed him hanging too. The new chapter just made it more clear because mafuyu asked if he would die for him and before that he said he'd do anything for mafuyu. Being in a drunken state, people do reckless things...
Here's the link of the pages connected with that scene to support Anon's comment above.
http://www.mangago.zone/read-manga/given/mf/v01/c001/2/
http://www.mangago.zone/read-manga/given/mf/cf00b0cee39d6b94b7bd4e3228e214c7_chapter-9/pg-12/
Notice the tumbled stool/chair on the lower right of the panel/page
I somehow missed that first page where it shows him hanging and the overturned chair. Thank you both. Poor Yuuki and Mafuyu :( But at least Mafuyu is starting to heal and Uenoyama kissed him! This was a very good chapter, certainly worth the wait. Thank you translation team!
Oh my god! I missed the first page! I know about Mafuyu finding him .. But OMG! This is ... my heart .. omg .. ╥﹏╥
aww maaan T.T that was .. idk what to say .. the story is still confusing but i just love it! i wonder if Yuki commit suicide tho? i don't think so! i'm so happy Mafuyu moved on even if just one bit .. and his friend is so cute xD he was like "what's with this face so annoying" and his face was also swollen from crying T.T mine too ╥﹏╥