Hi! I highly recommend sharing the ninjas you have so the community can pitch in some ideas with you! A screenshot of the list of your ninjas would be very helpful.

~Jib

Oh I see what you mean now. Terribly sorry about that. There are numerous ninjas you could go for, one of the good ninjas that many players covet and like especially in the "end-game" scene is Roshi. I highly recommend saving seal scrolls and using them during a seal scroll rebate to maximize your rewards.

~Jib

P.S. Your ninjas are quite good, especially Mei which from what I heard and experienced is an end-game ninja currently.