I found this fair-condition softcover at a local Savers thrift shop. (I enjoyed the Buso Renkin anime, which is pretty faithful to the manga.)

The story introduces the typical high school student and his potential love-interest, a strange girl who seems to spend her nights out fighting monsters. When he tries to defend her, he promptly gets killed - only to revive thanks to the buso renkin she's inserted in his chest. So now he has superpowers, of a sort - but also the responsibility to learn to use them against these increasingly-interested-in-killing-him monsters...

[The TV Tropes page for the series is what tempted me to watch the anime in the first place; entertaining tidbits, but do beware of spoilers.]

I left this, along with a few other books, in the charming Little Free Library at around 11 or so; hope the finder enjoys it!

*** Released as part of the 2016 TV Series release challenge. ***