Not gonna question why you want him so badly, but unfortunately there is noting to be done, everyone seems to have some characters that just never drop for their accounts. There are people in s233 who still do not have onoki from teh 5 kage treasure, there are people who somehow have got every ninja from the gnw treasure but have never pulled zetsu ( i know he is in the redeem shop now, just giving an example). The seal treasure is the first one you unlock and on the account I use to play in over the course of 4 years I never got chiyo 10 puppets. Sorry its not what you want to hear but no, there is nothing in your power to change drop rates from treasures unless his frags come up in events and you are willing to drop coupons you are at the whims of oasis own brand of "random" number generator shennanigans