A little concerning how “friends” is in quotes, in the original Japanese…

Ouma is leaving a veiled warning of sorts. This whole exchange was about her and Shuichi. Notably, he [cares for Kaede], but [doesn’t trust Shuichi].

What he’s effectively saying to her, is that false friends can be scarier than strangers. They act like they care, and are watching out for you, when they really just want to satisfy themselves and their own need for validation.

Whether they realise it, or not…