Toutarou Yamano is the younger brother of Eiko Yamano, a Garde pilot killed during Sidonia's first Gauna encounter in a century. Motivated by his sister's death, Toutarou joined the Sidonia Defence Force as a Garde pilot. Years later, he encountered Norio Kunato after Norio recovered from being controlled by the entity Ochiai. His surname Yamano uses the kanji for "mountain" (山) and "field" (野), while his given name Toutarou is written with the characters for "rice plant" (稲), "luxury" or "select" (汰), and "son" (郎), reflecting his heritage.