Yes and no. It concludes Touko's story, but also leaves two other character's whereabouts unknown. Sequel hook ahoy.
In case you want the spoilery details head over to my blog.
Edit: Yeah, actually, don't do that. You'll probably read it yourself eventually and I'd hate to spoil it for you. Needless to say it's a healthy mixture of happy endings and SUPER DESPAIR, as you would expect from IG.