I would like to apologize in advance for any spelling mistakes, and if this review is bad in any way : I will not compare this anime to any other and will give my honest opinion and tell my true feelings. It might feel biased, but eh, I love vocaloid and this game, so it's clearly made for me. Moving on !
This anime revolves around the game PROJECT SEKAI: COLORFUL STAGE (or Porject Sekai, if you want.) What is this game about, you may ask ? First of all, the game is a Japanese mobile rhythm game developed by Colorful Palette in collaboration of SEGA. Set in the real world where Virtual Singers only exist as fiction, the characters come across another world called "Sekai", where various "true feelings" are projected.
The game is set in the real world, specifically in the city of Tokyo and Yokohama. In this game, Hatsune Miku and her friends are famous fictional singers (who are indeed very popular in Japan, considered and receiving the fame J-POP artists do and loved by many) existing in the real world as Virtual Singer. They sing songs from creators all over the world, but they also exist in "Sekai," (セカイ) a mysterious world different from the real world that is created from a person's "true feelings", featuring various visual appearances based on the person. There are as many Sekai as there are emotions, and its form changes depending on the person's emotions. Therefore, the focus of the game is on the original characters and their journeys to find their "true feelings" with the help of the Virtual Singers.
The game features Crypton's Piapro Vocaloids: Hatsune Miku, Kagamine Rin, Kagamine Len, Megurine Luka, KAITO, and MEIKO. These characters take the form of VIRTUAL SINGER (formerly and still known as VOCALOID) and features 20 new characters that are split up into 5 groups: Leo/need, MORE MORE JUMP!, Vivid BAD SQUAD, Wonderlands x Showtime, and 25-ji, Nightcord de. Each of the groups has one or more Virtual Singer(s) advising them.
This anime is a compliation of short adventures of the five units presented before, except the characters are all chibis, with of course some cameos of the vocaloids. In short, it's just some of their funny adventures made into a bunch of short episodes ! It's cute, funny, and can help get to know the characters from the game a little bit better; maybe ?
If you're a vocaloid fan, or maybe you enjoy comedy, or maybe just want a anime to watch when you went to feel happy, or maybe you just want some cute chibis? This is clearly for you, then ! But of course, don't consider this to be a true anime with much "stortline" : this anime won't offer you any storyline. If you wanna learn more about the characters, then I suggest you play the game or read the wiki !