How do u know
Probably sign #1 was in ch 13 (i think?) guwon was vomiting after kissing teach. Maybe he's fully aware of how teach sees him and he plays along.
sign #2 is probably how secretive the people are about the past of the town. And how suspiciously scared they were when they are around guwon.
sign #3 is definitely the title. Sisyphus is known as a cunning king who was punished by hades by telling him to roll the boulder uphill, only for it to come rolling down again. HAHAHAHA the author is really sly
Oh gosh
hes a red flag. trust me.