Help me find this manga!

I'm trying to look for this manga. It's Isekai. Basically this guy got isekai'd into the forest, and to survive, he killed a rabbit (the scene was pretty funny). He found this cave/ruins and found books or something. Anyways, by reading those books, he instantly learned the magic spells and from there I don't exactly remember what happened. That was the entire first chapters summary, hope that helps!