Ro-Kyu-Bu!, Tenshi no 3P! Recommendations
Cute little girls being coached (or helped) by a high school guy.
Moe overdose warning. If you liked the lolis of one of these animes you will also like the lolis of the other anime.
Tenshi no 3P is not only just Ro-Kyu-Bu in a Jpop-rock band, they even featured the anime in one of the episodes!
Both shows you get enthusiastic lolis, and both of Kanae Itou's characters here are major-supporting characters who secretly loves the [boring] protagonist.
A teenage boy is tasked to help some little girls become better at something. In Ro-Kyu-Bu!, it's coaching basketball. In Tenshi no 3P!, it's playing rock music. Both anime are extremely cute and have amazing art. There's also plenty of fanservice in both, though Ro-Kyu-Bu's fanservice is a bit heavier.
Bunch of cute lolis surrounding a high school boy. And both the light novels were drawn and written by the same author and same artist.
Both based on the light novels by Aoyama Sagu and the wonderful art of Tinkle, with cute lolis that will melt your heart.
P.S. Lock Your Door!