Namaiki Asahi-chan wo Wakarasetai

Ryou is a third-year high school student who is enjoying his otaku life to the fullest, but one girl is giving him a headache. She's Asahi-chan, a cheeky childhood friend two years younger than him who attends the same high school! Even though Asahi-chan is his junior, she always teases and teases Ryou! And yet, when someone teases her, she is at a loss for words and makes a defeated face. She is also a cute girl who has few friends, is shy, and not very honest. Today, he has to teach this cheeky Asahi-chan a lesson!

(Source: Kodansha, translated)