"Mitsuki and Sekiei" (ミツキとセキエイ, Mitsuki to Sekiei) is episode 90 of the Boruto: Naruto Next Generations anime.
The damage Mitsuki inflicted causes Kū's body to begin to break down. Kū departs to get medical attention, but Sekiei prevents Boruto from following him with Explosive Clay. Mitsuki wants Boruto and Sarada to go after Kū while he deals with Sekiei, who is furious with him. Kirara blocks Boruto and Sarada with Akuta. Mitsuki tries to dissuade Sekiei from fighting so his body doesn't break down any further. Sekiei attacks Mitsuki, all the while accusing him of pretending to be his friend. Boruto and Sarada destroy a few of Kirara's Akuta, whose body begins to break down as well. Kirara brings out a gigantic Akuta to kill Boruto and Sarada. Boruto summons Garaga to help. In between discussing with Boruto, Garaga fights the giant Akuta. Sarada moves against Kirara, managing to distract her with a Sharingan genjutsu, giving herself an opening to land a Lightning Release attack on her. Kirara orders the giant Akuta to save her, but Garaga constricts it until it breaks down, one of its chunks crushing her instead. Sekiei continues to attack Mitsuki while throwing accusations at him, who denounces Kū's path, but thinks Sekiei can still be saved. Sekiei manages to get Mitsuki to fight back by threatening to kill Boruto. Mitsuki disables Sekiei's Explosive Clay with his Lightning Release. Sekki finds Ōnoki sneaking out, and explains he was sent by Akatsuchi. Kū reaches the doctor, but is informed the donors escaped, so he decides to get the doctor's heart. Mitsuki offers to take Sekiei to Orochimaru, but Sekiei is too damaged, and muses on how they are alike and how they are different, their feelings and motivations. Sekiei dies. Kurotsuchi leads the Iwa shinobi on taking back sectors of Iwagakure. Mitsuki catches up with Boruto and Sarada at the Old City, and they find Kū recovered with a new heart.
|Boruto Uzumaki||Yuko Sanpei||三瓶 由布子||Sanpei Yūko|
|Mitsuki||Ryuichi Kijima||木島 隆一||Kijima Ryūichi|
|Sarada Uchiha||Kokoro Kikuchi||菊池 こころ||Kikuchi Kokoro|
|Sekiei||Takehiro Urao||浦尾 岳大||Urao Takehiro|
|Kirara||Noriko Shibasaki||芝崎 典子||Shibasaki Noriko|
|Kurotsuchi||Hana Takeda||武田 華||Takeda Hana|
|Kontsuchi||Fumitake Ishiguro||石黒 史剛||Ishiguro Fumitake|
|Sekki||Keisuke Machiya||町屋 圭祐||Machiya Keisuke|
|Garaga||Masashi Nogawa||野川 雅史||Nogawa Masashi|
|Ōnoki||Tomomichi Nishimura||西村 知道||Nishimura Tomomichi|
|Kū||Subaru Kimura||木村 昴||Kimura Subaru|
|Doctor||Tomohisa Aso||麻生 智久||Asō Tomohisa|
|Akuta||Kensho Ono||小野 賢章||Ono Kenshō|