On 3 February, Kuzuha's cover of "KING" surpassed 10 million playbacks making it the the first video from NIJISANJI to reach 10 million ever, as well as the only cover of King reaching the milestone. It is also the most viewed cover of the song, reaching 10 million views in just 2 months, which is faster than the original which did it in 5 months.
On 8 March, Kuzuha briefly showed his 4th casual outfit (black knitted turtleneck sweater, and long violet overcoat) during his 3rd Anniversary Commemorative stream along with two new header and logo designs. Since there were two designs to choose from, Kuzuha posted a poll on Twitter to let the viewers choose which design they preferred. After the poll closed, the second design was chosen as the new channel header.
On 19 March, Kuzuha and Kanae both reveal their white White Day Night Party outfits in a reveal stream where they also revealed a new header and logo design for ChroNoiR.
On 9 June 2021, Kuzuha's cover of "KING" surpassed 20 million playbacks. A day before this, a viewer once mentioned that Kuzuha's KING cover was apparently used in one of their classes at school.
On 2 September, Kuzuha reached 1 million subscribers. He is the first liver in NIJISANJI and first male VTuber worldwide who reached the milestone. Despite being really happy for reaching a huge milestone in his career, and getting a lot of congratulatory messages and fanarts, he confessed that he did not prepare anything to celebrate it.
On 25 September, Kuzuha debuted his fifth 2D costume. The new costume has a semi-formal look with navy-blue suit jacket as the outer with brown knitted long-sleeved v-neck sweater on top of a black and grey checkered collared-shirt, coupled with black trouser and black shoes. He asked to use #くずはの布 hastag for sharing about his new look.
On 26 September, Kuzuha announced his participation in 7th Apex Legends Crazy Raccoon Cup along with Fuwa Minato and Ras (Crazy Raccoon).
On 28 September, Kuzuha's Day (9/28 can be read as ku-zu-ha) and the Twitter hashtag #葛葉の日 went trending # 1 in Japan. Kuzuha's first original single "Contrail" was released and reached # 1 spot on iTunes Japan chart and # 1 most downloaded song according to Billboard Japan. The original MV was also released on the same day.
On 31 October, to commemorate his belated 400,000 subscribers celebration and Halloween, Kuzuha revealed his genderbend form ー Sanya Live2D model with gothic lolita fashion style outfit, following the release of song cover "Vampire" which showing Sanya as the artwork.
On 10 November, Kuzuha revealed his 2nd 3D model with the same design as his "Contrail" illustration during his first solo birthday live concert "Scarlet Invitation". He also announced that he was going to have major debut under Virgin Music (Universal Music Japan) record label and launched his first mini album "Sweet Bite" on 9 March 2022.