Something where honestly Hakuno says weirdly girlfriend-y/intimate things too and constantly retweets Claudia's selfies but they're too awkward to make it a thing? For her part, Hakuno hasn't been in a relationship before and really wouldn't get what Claudia would see in her.

So yeah, slow-to-medium burn would work! They're incredibly close (and have probably known each other for a while) but there's a lot of things that'd make an explicit relationship awkward for them.