Swing Girls (2004)

Its from the same director with a similar story (zero-to-hero) and feelings : some loser guys discover synchronized swimming and pursue through hard work their new dream.

Pontifex Rembrary, a character known for his divine powers, gets transported to a new world while fighting a devil. He possesses the body of Woo Yeon Woo, a member of an unpopular idol group, and helps turn the group's fortunes around after a disastrous live performance. With his charisma and divine powers, he becomes popular among fans but faces challenges from his past, contending with strange religious groups and the devil.

Both has the name Swing, LOL
One is Japanese instrument, the other one is more serious Swing dance
Nevertheless, both are musical genre

Both are about the female lead involved in music.
The Japanese one in Swing instrument, the Korean one involved in traditional ballroom dancing.
They are both sweet and entertaining

Both are about high school girl band.
Beautiful Japanese musical movies.
Heart warming. Inspiration. Young talented youth facing many challenges

Both are about forming a band.
Both Japanese music related movie.
Many up and down , cute moment.
Fun watch.

Both are Japan movies about young people forming a Jazz Band.
Many challenges and obstacles.
Beautiful movie. Inspiration. Swing Girls has touch of Romance.
Kinds on the slope has developmental growth and romance involved

Both are old movies. Both are about forming a band
Both facing many hardship and challenges
Both band members love music and full of talented.