They are like a FAMILY of siblings! Sure, my dirty little mind want to slash Jin and Mugen together, but their heterosexuality always get in the damn way, and Fuu is just too innocent and cute to be put into a sexual position. Everytime I see them I just want them to keep on going and going and going with their journey, and NEVER stop because they just have this wonderful relationship that should NEVER end!!!

(But on a purely theoretical way, if Fuu were to become more mature and if Jin and Mugen would fold under the sexual tension I'm all for it ^__^V)