After seeing the first episode of the anime I started reading the manga and my first suspect was the teacher (i don't know why) but the more I read the least I suspect because he was so helpful and ... but now I'm just shocked, they say "Piensa mal y acertarás" which can be translated as " Think bad and you'll be right".
I want to believe that Yuuya survive and is living somewhere out there like a good infected without eating anyone. (╥﹏╥)و