if one plans to do tree you must decide early in the first 2 days of the event, because you will be able to fully redeem the power options as there are daily limits. For me asura turned out to be 1 frag per 1500 coupon spent but still it was the best choice for me as a f2p to get his frags. I got equal amounts asura and black zetsu and with the fuku pack enough to 4 star asura. Shisui definitely is lower drop rate. If you decide too late, there are next 2 weeks to see if those events are good to spend for this 110k fuku.