well two of those posts are targeted at specific comments but could've stopped with 2-3, i digress. I don't post a lot, and I'm excited to help since I'm familiar with the game.
Knowledge Items (unlocks Passives and skills)
Director of Fine Arts Club Maya- unlocks Concentration skill. You can fight her I think after the first weekend tournament, she happens to take part in the tournament.to help build her confidence in fighting.
Yuko (Director of Gymastics club)- unlocks Balance Passive which helps you not trip against certain kicks, Shes in the room with the Rhymatic Gymist Girls but shes not one of the hostile ones, you have to go talk to her specifically when you unlock the Gym.
Chiaki (Director of Drama Club),unlocks normal mind passive ( i think, which reduce mental damage/excitement i think)Shes one of the two people you can fight in the Drama room but isnt the Teacher.(WARNING the teacher in the Drama Room is a one loss game over so be warned should you choose to fight the teacher, she is a completely optional fight, and only gives a couple Drug Tickets,)
Nanase (3-B) Unlocks "Passive" passive (which reduces Throw Damage) You can fight her by losing to the Judo Club leader (one of the Badge holders) and bribing Nanase with the Mixed Sandwich which you can buy on certain days ,After which you allowed to fight her till you beat her 3 times.
Chiyoko (Volleyball club) Unlocks Patience passive( forget what this one does, i might have it mixed up with peace of mind) Fight Volleyball captain in the gym during last 15 Minutes of the day, if go too early,shes busy with practice and wont fight with you.
Seiko (long distance track club )Stamina Passive (More HP) Shes running in the screen with the front of the school, the back of the school is the screen with the short distance Track girl that has the Badge .but again,screen with thefront of the school and shes on the left side of the building , you can nearly walking to the back end of the school to find her. Shes NOT the loli.
Sakuya (Archery Club Captain) Spiritual unity skill (reduces excitement by 100 instead of 50) Shes in the same building as the Judo Club but opposite rooms.Judo club is on the Left most, Archery is on the right most. Shes the one with huge boobs and a pony tail as opposed to the girl with twin tails. As Far as i know you can just challenge her even while her club is active.
Kick Defense (Library bookshelf)(Kick Defense passive reduces kick damage) its being blocked by a girl in the Library, you have to beat her before she moves but she wont fight you unless your Pride is below 50. The Simple way to reduce your Pride is to equip masochist skill which reduces your Pride below 50, Alternatively let yourself with humilated by a bunch of girls or have sex with Nana who raises Mental Strength at the Cost of Pride repeatedly.
You have to completely defeat the girls (beat them 3 times) to unlock the knowledge.
After you get the knowledge for these passives you have to do a corresponding Training to unlock it. I'm not sure which Trainings unlock what but i know Jump Rope applies to multiple.
Masochist is a weird outlier. Someone said that they unlocked it off using the childhood friend clothes, i didnt unlock it till i had someones underwear after i lost to them and gameover'd and used it TLDR use girls underwear/etc when you masterbate at the end of the day.