Omotesando Koukou Gasshoubu (2015)

Both have unlikely friends bonding through club activities. Both are heartwarming and addictive.

Similar story about a choir group. And have a love story like the drama series.
Recommended if you like something related to music

Both about teacher in the city went to a small town or village. Both children were talented in singing. Heartwarming musical film

Both films were about choirs. Both have beautiful voice. Both were women from different background. Universal music touches people hearts

Although My Paparatti was about a singer young man with beautiful vocal cord, and powerful voice, both movies about classical music.

both took place in a high school, with a theme of youth and togetherness, both emphasized love for music as a path for unity, lacks romance but it hits you in the right place through the heart

Both dramas are centered on a chorus which is to overcome certain problems (that goes without saying) as a whole but also as separate individuals. Some of the songs are even the same in both series :) ! The main differences are the age bracket of the choir's members and the fact Kaeru no Oujo-sama is also about dancing ;) !