The original title (Ki wo Tsukae!) is a pun, meaning both "Use ki!" and "Be mindful of others!"

This homonym isn't a coincidence, since the same word 気 refers both to ki in the mystical sense and to a person's general awareness. So telling someone to be mindful of others is telling them to "use their awareness", in the same way that telling someone to be careful (ki wo tsukete) is telling them to "attach their awareness". Of course, the difference between using and attaching your awareness might seem meaningless if you think about it too much, but idioms are what they are.

I spent a while thinking about puns using "ki" to replace the word "key", like "Caution Is Ki!" or something, but then I remembered that the fandom generally uses the Chinese-based word "qi" anyway, which is pronounced chi. So I decided to drop that idea and go for a less elegant but at least snappy word replacement.