Actually there no accident when she got summoned, if not, she will be involved in car accident and die for real. And ” Onii-chan” not as pure as he seem, he’s a Yandere
and lolicon through and through with sibling complex tendency. And the MC accidentally said forbidden words everytime she drunk with him so that seem to make him more and more possesive of her, beside the ML know a way to calm her down everytime (what a reliable onii-chan). And~~~~ there will be smut scene in the end…. You’ve been warned.