First things first, know your worth. If he is this indecisive then he is not worth your time nor your mental/emotional space. There are people in the world that are a much better investment of your time.Trust. As well as everyone has a certain bandwidth in their lives for multiple things, time, emotional, etc. Choose wisely on who you want taking up that width.
But if you want to get to know him as a person, just talk to him. Doesn’t hurt to be the one to take the first steps. Actually even better cause it puts you in the driver seat of the conversation. If he responds with the same interest and energy back. Then maybe he is someone who is worth space on your bandwidth. Obviously keep in mind people can be busy, though if they are always busy also keep mental note of that as well. Also if after getting to know them more you feel like you are always initiating the conversation and putting a noticeable amount more effort. I would reevaluate if they should just be casual friends or if I am willing to spend any more effort than that in general.
All in all, if you put in an obvious effort and he still is acting the same. I would put the ball in his court and let him decide. In the meantime I would move on and work on myself. Either they will make a decision at that point or you’ll make it for them by moving on.

Guys there’s a boy who’s like the duke (not interested then interested) in me just when my crush for him had died. I wanna know what’s he up to and I need research and any help possible.
Any other mangas like this one who could offer advice on how to keep the male lead in pause ? (I don’t want a relationship but I want to know him more)