Hiii, I read this manga a long time ago and had forgotten its name. Google isn't helping me quench this curiosity. The beginning of the manga starts with;

• a guy got accepted into a school which only accepts students who can see the floating island in the sky
• on their first day, they have to write a kanji of what they think would help them survive and the MC wrote "change"
• then the blight (i think that's what they called it) begins, monsters everywhere and the students have to rely on their powers to survive. Thank you!!

i think it's Aphorism

OMG thankyouu!