That's a good idea. With all the knight training and questing experience under your belt I bet you'll kick his ass now, Jean.

[Unless Eren being from a later point in time than Jean means that he learned a bunch of new skills as well...]

But honestly, just do what you've done back home with him. Even if you two butt heads, isn't it alright?

[He really isn't the best advisor on healthy, normal friendships, given the insane levels of roughhousing that happens in the Shinsengumi.]