Man, I don't hate that Sunbae but I hate that smirk. Watchu planning, you yellow haired ma...

I think he was just smirking cause he saw Lotus and thought how cute hyesung and lotus's relationship is? if that makes sense..I'll try and explain it like this, I think sunbae just thinks it's funny how lotus is there to make sure nothing happens between them (sunbae and hyesung) and he recognizes how great of a partner lotus is. sunbae doesn't seem like he has any bad intentions, I think hes a good person and just cares a lot about hyesung.