u/Emplois_Muswashans

Yeahh I only remember this part of the anime where mc backstory with his sister.. Mc, sister, and 12 other students got stranded/crashed in a mountain that they don't know so they had to wait for rescue... They planned to gather some resources and like got some plants, veggies and carrots... Mc (I think) ate one of the carrots in which he was afraid that he would be scolded harshly so sister stepped up and told him a secret on how to turn the 12 carrots into 13 again... After a while someone discovered a mushroom or like some food (I forgot what it was) in which everyone rejoiced except the sister cause she has a bad feeling about it (she was right). The sister didn't eat the food with the bad ingredient and also didn't let the mc eat it.. The food the other students ate was actually like a virus which turned them addicted to sex/ like made them zombie like... The mc and sister( which was not infected) ran away but the sister got caught and got bitten in which the sister said to the mc that he should run! Mc ran and ran and ran until he found a field and ate some cabbage... Backstory ended and mc said that his sister might've still been Alive because 13 bodies were found but all of them had a missing head/limb in which was familiar to how his sister demonstrated to turn the 12 carrots into 13

I slightly remember that mc has a colored hair(def not black) and goes to an academy that battles using mecha/robots.. In episode one, mc was introduced by the principal to his peers(all girls and one of them had pink hair). He battles the pink haired girl (which was like in of the best mecha soldier with a good mecha) and almosts win using a common one until an enemy invades the school and they have ti halt and battle them... Girl with pink hair battles like the commander and is about to be obliterated until mc reveal his op mecha and defeats enemy... The thing is that the mecha was the one that caused a coup d'état in the past thats why the mc was reluctant to use that