My Friend's Little Sister Has It In for Me! - Season 1

For high schooler Akiteru Oboshi, the whole youthful experience thing—like fun, friendships, and even having a girlfriend—is a complete waste of time. So when his best friend’s sister, Iroha Kohinata, keeps teasing him, Akiteru naturally finds it annoying. She practically lives in his room, she’s always on his bed, she’s just a raging storm of clinginess! Why is she only annoying around him?!