On 23 February and 9 March, he appeared with Nui Sociere as guests on Episodes 5 and 6 of "NIJISANJI's Class B Variety Show (Tentative)", hosted by Ibrahim and Hayase Sou. This fulfilled one of Kagami's goals for the year.
On 26 March, he became the main host, disciplinary committee head, and prosecutor of the segment "Help! School Trial" (Part 1, 2).
On 3 May, the full version of his original song "WITHIN" reached 2 million views.
On 10 May, NIJISANJI's first 2 voice dramas, "Kurogane no Folklore" and "Singularity Oratorio", were released. Kagami played the role of "Hayami" in the former.
On 11 May, an official live viewing event for the Gundam film "Char's Counterattack" was held at Nico Nico Live Broadcast to promote the film "Mobile Suit Gundam: Hathaway's Flash."
On 22 May, he unveiled his new costume which was based on the Zepp Fukuoka key visual for "NIJISANJI JAPAN TOUR 2020 Shout in the Rainbow!" (design by Aiko Batsumura). In addition to the different layers of the original outfit, a new hairstyle was also added.
On 11 June, he premiered "the MV of his original song Tremolo Moon". The premiere was launched without warning in the middle of the night, despite expectations that "PIERCE" would be released first.
On 29 June, he premiered "the MV of his original song PIERCE".
On 3 July, SMC-gumi commemorated their 2nd anniversary with a collaboration stream. During the stream, Hakase and Yorumi read the letters that they had originally prepared for Day 2 of "Kyo to Aki no NIJISANJI".
On 6 July, to celebrate his 2nd anniversary, he featured a special project that he had been working on for himself. He commissioned award-winning Gunpla modelers (modeler: Re-ta, painter: tanakamushi) to create a custom Gunpla based on his angel costume.
From 17 July to 15 August, he participated in and won Power Pro "NIJISANJI Koshien 2021" as the baseball coach of Kagami Business High School.
On 31 August, the 3.0 brushup of his Live2D model was announced. He later unveiled it on 17 September. Aside from improved motion, particularly in forward and backward movements, the update also featured four alternate expressions that he showed off on stream. (At the time of release, only the default costume had been updated to 3.0, with other costumes to follow).
On 17 September, it was announced that SMC-gumi will feature as in-game cards, skins, and accessories for the 2nd NIJISANJI x Duel Masters Play's collaboration. In addition, Kagami recorded a new original song titled "Kagiribi" that featured in the game as duel BGM (excerpt here). A full version will be released on his channel at a later date.
On 21 October, it was announced on NIJISANJI YouTube channel that Kagami, Kenmochi Touya, Fuwa Minato, and Kaida Haru were debuting as a unit under the name "ROF-MAO" (ろふまお). They have their own official YouTube channel and Twitter account. They launched their regular program called "ROF-MAO Juku" (ろふまお塾, ROF-MAO Cram School) on their official channel.
On 1 December, Kagami held a stream to countdown to his 30th birthday. Here, he showed some of the gifts he received, his questions about turning 30, the damage he received upon turning 30, and tickets to "Happy SMC Party."
On 3 December, following the birthday commemoration, his first three original songs, "WITHIN", "PIERCE", and "Tremolo Moon" became available on various streaming services. On the day of release, iTunes ranking sales among Rock TOP SONGS in Japan for these songs rose to 3rd, 6th, and 5th, respectively.
On 5 December, he reached 450,000 subscribers on his YouTube channel.
On 13 December, "SMC Party" presented by Magic Lab (Yorumi Rena and Hakase Fuyuki) was held. Kagami was given various challenges to test his physical and mental strength in his 30s. The girls gave him various presents and Kagami gave back thank you presents as well.
On 14 December, SMC's cover of "Sugar Song and Bitter Step", currently the most viewed video on his channel, reached 8 million views.
