Zettainaru Kodokusha Light Novel Series by Reki Kawahara

Minoru Utsugi, a teenager who lives a peaceful (if boring) life with his sister-in-law, finds his life changed when extraterrestrial contact grants his dearest wish, leaving him with the power of The Solitude. But the ability to realize absolute isolation only plunges Minoru into a battle he never wanted to fight. As his old life comes to an end, he steps into a new role...as the Isolator!

An alien parasite living inside of Minoru Utsugi gives him the power of Isolation--an unbreakable shield that surrounds his body. With this power, he's managed to defeat an evil Ruby Eye. Having done so, he's invited by the Accelerator--a girl named Yumiko--to join a mysterious organization, whose goal is to defend humanity from the threat of the Ruby Eyes... moreAn alien parasite living inside of Minoru Utsugi gives him the power of Isolation--an unbreakable shield that surrounds his body. With this power, he's managed to defeat an evil Ruby Eye. Having done so, he's invited by the Accelerator--a girl named Yumiko--to join a mysterious organization, whose goal is to defend humanity from the threat of the Ruby Eyes. Minoru agrees to join, with one condition: Once he has fulfilled his duty, the Syndicate will erase all memory of his existence from the world--for Minoru seeks a world without any knowledge of him, a world of total and perfect isolation.But his next enemy is cunning and deadly, with the ability to manipulate oxygen itself: the Igniter. In the face of this all-consuming inferno, what will become of the Isolator? less

Having successfully helped destroy two of the evil Ruby Eyes, Minoru, the Isolator, is recruited by the Syndicate, a secret organization dedicated to their eradication. He teams up with Suu Komura, the Refractor, a young girl said to be the Syndicate's most powerful member, to attack a secret stronghold of the Ruby Eyes. Their target is the most fearsome opponent they've ever faced: the Liquidizer, but their enemy is not what they expected...

Though the infiltration team narrowly escaped Liquidizer's cunning trap, no one knows if Suu Komura will recover from her appalling injuries. Minoru begins to question whether all this suffering is worth it. Unfortunately, there's no time for him to be indecisive when someone known only as the Stinger launches brutal attacks at Jet Eye and Ruby Eye alike!