Demon Slayer in every situation

Training you in Total Concentration Breathing

Tanjiro: *You spend all day listening to him making weird noises and waving his arms around* First, you need to go like: "Whabaaaaam!". And then, you go "Babooooom". That'll make your heart go "ba-dum, ba-dum!" And then.... *All... day... long...*

Inosuke: *Basically, he has you follow him around, fighting everything, and hopes you pick it up. It's a surprisingly efficient teaching technique*

Zenitsu: *If you're a girl, he asks you to marry him. If you're a guy, he only gives you a quick run-over, then goes back to the girl*

Nezuko: *You asked the wrong person*

Kanao: *The training will be hell. You will probably die. Don't start with her*

Giyuu: *A pretty good teacher, all things considered. He just... doesn't know what to do with you*

Shinobu: *One of the best options. She's kind, but strict. Strong, but thoughtful. She's an awesome teacher*

Tengen: *You have to venerate him as a god, first. Then, you need to follow his routine, and strike a dramatic pose at the end of every exercise*

Rengoku: *Probably the best teacher. He's not gentle, but he's the nicest one and will never give up on you. He's loyal to you and everyone likes him. He's the best choice*

Iguro: *He ties you to a tree and beats on you until you manage to escape. Not many people survive this training*

Mitsuri: *You're gonna need to wear a dorky outfit and be extremely flexible to be able to keep up with her. Also, you're probably gonna want to be handy with a whip*

Gyomei: *Almost nobody can finish a training as intense as his. Boulder-pushing, waterfall-standing, log-lifting, ball-on-chain-swinging. You will probably give up before finishing*

Muichiro: *Has you repeat the same exercise until the building around you literally collapses. You're gonna want to get on his good side, fast*

Sanemi: *You try to survive. It's literally a week-long exercise in which you try to survive, and he tries to kill you. Good luck*