The Day I Became My Sister

After an unexpected accident, distraught Tsubaki Tsukishiro is left in denial of his sister's death. But after a moment of despair, he has an epiphany, *"I don't need to exist if my sister is here."* Donning his sister's clothes, he ventures out with the resolve to erase the existence of Tsubaki in favor of reviving Chika. But while passing through the streets on the day of her funeral, a man calls out to him with a single word, Chika?