"Boss... thank you... for everything," - Akaba's last words, before handing Kazumi Sawatari his dog tag.
Akaba
(赤羽 Akaba) is one of the minor antagonists in Kamen Rider Build. He was born as Masaru Ooyama
(大山勝 Ōyama Masaru, but after being experimented on and joining Kazumi Sawatari, he was given the name Akaba, thinking that Kazumi would actually refer him as so. Later in the series, Akaba becomes part of Sento's team, after Kazumi lost the proxy battle. He uses the Castle Fullbottle to transform into Castle Hard Smash. Later on in the series, he gets upgraded into Castle Hazard Smash. He is portrayed by Eishin.
