As the title says, here are the tips to get 100% CG on JAST's new SRPG: Yumina The Ethereal
General guide to get all the CG's:
*Note: Keep in mind if you surrender during the debate battles you get the option to start the chapter over with all your money,stats, and quests still done. You're meant to use this feature if you don't get a skill in time for the boss fight. The only thing you'll lose are skills gotten through events, so you need to do the proper events again.
Also, if you want to H all the bosses, you will have to do the conversations events all the way up to Day 9-10 and that just leaves you with 1 turn to train in the Dungeon Game before the debate battle.
Chapter 1: Just keep going to all the meetings and the Librarian events. Eventually you'll get the skill after the event at the GYM. It's a buff. Make sure to use it in the debate battle, this is important for all the boss battles.
Chapter 2: Tomori's scenes are the hardest. There are a ton of events you have to do and the fastest you can get it is Day 9. Do all the events with Rei and Tomori that you can. After that do an event with Yumina in the library and Ai in the club room. The Yumina event will unlock an event in the Dorm and the Ai will unlock a "?" event at the gym. When those are done, once again do all the Sis/Bro events that appear. You'll eventually get a Tomori event in the cafeteria where you get Sister Blade. Use this on the boss and you will get the CG.
Chapter 3: Easy. just keep on talking to the Mikos and going to the meetings. You'll get the skill Independent Heart. Use it on the debate battle.
Chapter 4: Also easy, but you have to choose the right choice. Talk to the Blond girl every chance you get, keep going to all the meetings, eventually you figure out her weakness, when you tell her, she'll beg you to keep it a secret, answer that YOU CAN'T PROMISE THAT. Afterwards there is one last meeting where you'll gain the skill Absolute Horizon, use it on the boss.
Chapter 5~8: These are chapter related to each path. The path is chosen by who you talk to on the holidays. There's a lot of free time so you probably don't have to worry about missing any scenes.
*There are 3 difficulties, Normal/Hard/Super Hard and you need to be on a certain difficulty in order to unlock more of the Training events. Just keep on doing the main missions and you'll eventually get them all.
*Harem: The harem ending requires you to H all of the bosses(Tomori for CH2), and then not qualify for any heroines route afterwards.
*Finally: There's a special play that happens once you get all the medals. (Complete the 3 paths and all of the Training missions).
*100%: To get a technical 100% you need "ordinary" and "true" routes of all 3 girls + ordinary "graduation" ending + school harem ending.
Sounds like a lot, but once you get the first play-through and harem ending out of the way it's just a matter of running through the boring as fuck fights with different scenes. Just keep beating it and you'll get there, should be a trial of patience at this points since you will need to do all battles again.
Hope it helps, enjoy!