I am looking for a certain anime!?

i saw the beginning of the anime at one point and remember parts of it, a teenage guy is the protagonist. in the beginning there was a girl who was in a construction site and uses a invisible monster of sorts to kill the people there. The protagonist is attacked by another teenage male that talks about the invisible monsters but has no clue what he is talking about. there was a bit of a slaughter of a few people in a court yard by the teenage boy very gory scene where the people are cut in half. if im not mistaken a young girl walked up to the protagonist before everyone was killed i cant remember details >.< eventually later in the episode the girl from the beginning and the teenager that has been attacking the protagonist fight and the teenage male looses an ear from the girls invisible monster if im not mistaken. (at the very beginning there might have been a scene that had 3 children in a Field 2 girls and a boy cant remember details but right before the anime really got off the boy was kissed on each cheek by the girls **i don't know if this is from the anime i was describing earlier so i included it last) please please help as much as you can i have been trying for a while to find the name with no luck :(