Depends on your play style. For me, No.

Nope.

Not worth it for lightning main. If you plan on using other mains in the future and want to stay competitive, sage could give you a really good head start. Keep in mind that the longer the game goes, the cheaper and easier sage will be to obtain, so now you'd end up paying a lot more for an early access. That being said, if that early access could help you dominate pvp field on sage/arena ranking, getting more refines and ninja fragments might turn out in a good way. 10k is really expensive though, currently on english version you can get him for 6k coupons (so considering u can transition ingots into coupons over time via try your luck or convoy, its 2k ingots).

Ask yourself: will i play other mains? Do iI have a team for him? Will getting this ninja affect my pvp in a meaningful way? If I overpay, will I dish out enough off of his value to make up for it?

If the answers are yes to all, go ahead and buy him.

thanks mate! really helpful answer