Every race in Kandagawa Jet Girls starts with you leaving everyone behind on the starting line and then never seeing them again. The single player mode might as well just be Time Attack. 
Supposedly some of the later character stories get more difficult, but I haven't gotten that far yet. Looking at just the game play, it's not very good- too easy, track design is "eh," and it's not like anyone is going to be doing multiplayer. But add in the story and other wacky stuff like the mini games and it's fun enough overall for what it is.
What was released was apparently not what they intended the game to be- Sony's policy changes forced them to leave a bunch of stuff out. Originally there was going to be a much bigger focus on the watergun combat (with exploding clothes, of course).
I don't get why the developer's response to Sony has just been to give a sad "we had to cut our games. It can't be helped" instead of giving them the finger and releasing the games as intended on other platforms, or just cutting whatever content for PS4 and releasing them uncut on PC/Switch. It worked for the Omega Labrynth devs and with niche games like these, the consumer base likely already has the other platforms or will go buy them just for these games.
