Hrm... I can't figure out Yuki's last line. 自重すべき means (as far as I can tell) "should be wise/prudent" but that doesn't really fit...

自重 means "not taking oneself lightly", ie "being mindful of the circumstances and avoiding doing things that could damage oneself". In Japanese culture, especially when used as an admonishment, that means "do not do things which would damage your social position, or your standing in the eyes of others".
Since I couldn't think of an English word that precisely describes the concept, I paraphrased the sentiment.

The other note was wrong too.

Ah, "Yandere Only" is an event? lol that makes a lot more sense...