Idol Shikkaku

Keita, a boring university student, is a "gachikoi" (fan who's seriously in love) otaku of Mimika, the center of the idol group "Tetra." Even though he's aware that it's a love that will never happen, he continues to push on with giving her his emotional support.

On the other hand, as her group's popularity continues to rise, Mimika bears anxiety over the uncertainty of the future even while she's happy with the fervently cheering Keita's affection. One day, Mimika falls into despair after her mother gets into a traffic accident, and with the help of social media, she heads towards Keita's part-time workplace...

(Source: Kadokawa, translated)