just save man there still no good ninjas on treasures o this era of the game just few ones with bt

you have to wait when there is event about that

i always take the frags of them and summon scroll from groceries storage room you need sun scrolls for that

and there is 2 weekly on monthly event and the reste come by it self and some events

sometime you get lucky by get it from survival trail and sealed ninjas and there is ranked arena and theme arena too