Sword Art Online: Phantom Bullet, Vol. 4 (manga)

This might be a game, but it’s not something you play.
Determined to put a stop to Death Gun’s killing spree, Kirito and Sinon are competing in the Bullet of Bullets tournament. With only six players remaining, the stakes are higher than ever, and Sinon knows the only way to put her traumatic past behind her is to take Death Gun down once and for all. But after Kirito starts to suspect a real-world accomplice is involved, the situation gets even more complicated…How can Kirito and Sinon hope to win against two murderers in two different worlds? The action heats up in Phantom Bullet’s thrilling finale!