Entire school bus of students die and isekai'd.
MC only one isekai's as human.
Imouto isekai'd as vampire and kidnapped by vampire lord.
Classmates also isekai'd as monsters.
There were 21 classmates so it seems to be a "catch them all" series as they find more of their isekai'd classmates.
Don't know how I missed this one but I'm interested.