Wonhagiman Haeseoneun

Noah, who fell in love with the older twin brother, Louis, and moved into the house where the two brothers lived. Until then, Noah got drunk and slept with Lucas instead of Louis. Feeling threatened, persuaded, and secretly attracted to Lucas, Noah ended up spending the night with Lucas for about three months without Louis knowing. The relationship between the three of them, which had been peaceful, changes one day when Louis sees the two of them...

(Source: Ridibooks, translated)

Note: Part of the Geogeoikseon: Heavenly Original Webtoon Danpyeonseon (거거익선~헤븐리 오리지널 웹툰 단편선~) Collection.