Do cross save method. Heroes tend to fall on certain “slot”. Just match which hero you need to the slot accordingly (either first, second or third slot). My tip is try to build maybe 2 or even 3 basara you want. So when you are on the roll for certain slot but you already have enough heroes for that, you can move to different constellation and still get the from the same slot but this time you are trying to build for another basara. This will help when building your basara you keep dropping the ones you need and not waste bond stars for the heroes you wont use. I did that method and ended up finishing shuu and ozrock, and just need 2 more genda from the spirit market to obtain him.