The survivor was 5 peoples
1. Kakuta (the 1st/2nd missing person)
2. Fukuyama (the 1st/2nd missing person)
3. Sasaki (the 3rd missing person)
4. Inoue (the 4th missing person)
5. Sugihara (the main character)
i don't know who is the girl, but for sure, this manga didn't make my thingy hard...