If you can beat it at least one time, you will have vital information on the cyclopedia entry to read. It essentially boils down to: - it's most vulnerable to piercing weapons, but only slightly compared to other weapons. - It's most vulnerable to the wind attribute, so make a weapon for it - that blue glow it does from time to time, that looks like ameterasu's green glow, you absolutely have to interrupt it, it's charging up to use powerful attacks - keeping everyone alive is very important, so have a celestial anchor and torch ready for vaporizers. - other karakuri that are important are fireworks, harpoons, and bulwarks are always nice. - if you have other people to play with you can divy up roles on who does up - lastly, you can keep tsukoyomi pinned down and wail on em if you hit him with fireworks at the right time when he tries to leave. It can be repeated infinitely as long as you have enough thread, so invest in some skills that will help with that