The Commander is the main protagonist in Azur Lane Mobile who serves in factions. He also appears in the anime, but he was only mentioned a couple times and never made a full appearance. He is also one of the most important characters in some of the official mangas.
He's not top brass to fill the role that he does and "commander" is more his role than his rank. He is also meant as a insert character so he's likely a young man, too young to realistically be an admiral. He is call "shiki-kan,".