Arang did like Sekyung.
Using his masterful stage skills, he forms the Cyrano Dating Agency.
Should they persuade the boss to give up Operation: Idol? He is the loan shark who originally lent the money to Do-il for the Cyrano theater, and is later revealed to be Do-il's younger brother.
It just feels like sudden flip-flopping after a matter of a few days when she's been watching Arang for a while.
It is also this scene where Hoyeol injures himself, and its the bit where Se Kyung applies the band aid on his hand.
He sinks into melancholy thoughts, and looking at that Sherlock Holmes charm triggers a flashback of when he first received it.