hardly.
Rare Nins will drop every six 3* Ninjas (~60 pulls)

Thats gonna take a long time before i can do that :/

If you are really full on f2p then yeah, it's gonna be a rough time. But if you spend just a little (enough for the monthly card and daily spins for coupons on the wheel) and you save all of your scrolls until level 70 sage treasure, then you should be able to do a 6x10 pull which gives you a chance at naruto (about 33% chance).

Even if you don't get him, the other two rares in the sage treasure are really good and worth it. Don't bother with the pains, too many rares to draw from in that pool.

Someone in my server said u have a chance getting one of pain 40-70 except Tendo.

It's definitely doable for f2p to get Rares. I didn't buy a single seal scroll and just saved the ones from the events, GNW packs, Matsuri etc. Had enough for 6x10 pulls in a little over 3 weeks. Sure, it takes time but it's doable. It's super rares that are practically impossible considering they need around 400 pulls.
Oh and btw your Free pulls every 2 days still count towards those numbers.

just stack up 160 scrolls and you will get all the ninjas (rare) in sage treasure, dont waste any of them from lv1 to 70

While it is possible to pull a rare like that; Don't expect it to ever happen. But a "fixed" drop will appear anywhere from 40-70 seal scrolls used in a particular treasure set.

Best of luck and good fortune for it happening and may someone be looking down on you blessing you.(Curse you RNG Gods they hate me! :@) But there is a very minuscule chance.

It is definitely possible. I'm completely f2p and managed to get Pain-Jigokudo

Well i already bought the monthly pack because it is really worth the price, but until i saw that waiting for 10 scrolls is better than doing it one by one, so this will be my first multi at level 70 which is terrible i know, so should i aim for sage treasure from now on ?, oh and my group cant participate to gnw so no seals from there :p