Shidō Ryusei is one of the strikers from Blue Lock. He played as an extra for Japan U-20 who was picked up by Sae when he was arrested for committing excessive violence against one of Blue Lock's other strikers, Rin Itoshi, Sae Itoshi's younger brother. He was allowed to go crazy on the soccer field by Sae, and ever since then he has liked Sae. He even wanted to ask for Sae's number and he was talking like he wanted to stay with Sae or play soccer forever with Sae.