Hopefully the thing about keeping their relationship as a secret gets dropped soon. I perceive drama coming from this because that's kinda expected to happen, lmao :'). Although, I understand Soyou not wanting to be in the spotlight for unwanted attention (especially jealousy) since Jaeha is kinda popular with their classmates.
@forgettingforgetting
Maybe it's because Ahin is in the unknown about why Jaegyung is not coming (or found? iirc they all think that he is going, but is nowhere else to be found?) to school and his current situation as a shut-in. Remember that Jaeha took his "role" in an event unrelated to school just to not rise suspicions, since Jaegyung's family seems to be well-respected and the like. If Ahin finds out that they are indeed related, she could be getting answers as to why he hasn't been going to school and their whole family situation as well... and it might not be pretty (and a bit invasive from her own perspective as an outside party), tbh (regardless Ahin's, maybe?, intentions to help Jaegyung if that was the case).