Miyoshi is a teenage boy of average height. He has short brown spiky hair. He also has black eyes. He also has a rather dark skin complexion. He is usually seen wearing his school's uniform, a dark blue blazer and dark blue necktie with white stripes over a white polo and gray-blue pants.
- (To Osamu) "Border's regular members all have their names mentioned on the information site! I know all of them by heart!!" 
- "Miyoshi" (三好?) means "three, virtuous".
- His Japanese voice actor, Yūsuke Handa, also voices Hidehide Hinoe, while his English voice actor, Nick Wolfhard, also voices Shun Midorikawa.