~かい
It’s an informal question marker. The answer to a question with かい at the end is YES or NO (you don’t need to provide any explanation; you can, if you want to)
か alone is an ”open question” and usually people give some sort of explanation to a question ending with か
It also sounds softer than か
Your superiors may use it with you, but it’s not the best idea to use it with your superiors.
Between friends, it’s ok.
It’s mostly used by men (manga/anime are exceptions).








