Are there  no quests through it?

I've been wondering the same thing. I did the small quest of getting Masou's parents together but haven't been able to find anything else to do there. I've gone around with the flower lamp and UV light as well as trying to advance dialogue with Masou's mom using the portal at home base but was unable to figure anything out.

For now that's all that can be done.

As someone mentioned there's only one quest there. It's not completely implemented yet. Delivering letter is part of a quest.