Shukusei no Girlfriend -the destiny star of girlfriend-

When campus nobody Seiji is attacked by unhinged space demons, it’s his classroom crush Yuuri who shows up to save the day! Her magical-girl powers easily vanquish the enemy, but a surprise ambush forces her to dive in harm’s way to shield him—leaving both fatally wounded. Luckily, Miss Fujiko arrives on the scene with an enchanted thread to bind both their life forces, saving them from certain death. Over the next three months as Seiji and Yuuri slowly recover, the pair are on doctor’s orders to stay within one meter of each other or risk snapping their “red string of fate.” This means shacking up together and pretending to be a couple to avoid their classmates’ suspicions, but despite the clueless Yuuri claiming to be a “one-woman fortress with zero openings,” her natural powers of seduction quickly result in awkward situations that test poor Seiji’s sanity and self-control... With his dream girl only centimeters away at every waking moment, will Seiji finally summon the courage to shoot his shot?