This is an official music video from a game franchise called IDOLiSH7 (which now has an anime), so please take a note that this is not a show, this is a music video. If you want to know their true stories, please watch their anime or read it from their game. This music video doesn't have any deep story, this is just like any other music videos in real life. It only shows 7 guys from an idol group named IDOLiSH7 (or i7 for short) which singing and dancing on their stage singing this song. And some scenes where they have fun together, fishing, making cakesand foods, etc.
This song is so cheerful which I like, and they using CGI on this music video which is really good and smooth.
So for you who already know or even like i7, you'll probably enjoy this music.