Arpeggio of Blue Steel (蒼き鋼のアルペジオ, Aoki Hagane no Arpeggio) is a Japanese manga series produced by Ark Performance and serialized in Shōnen Gahosha's Young King Ours. 27 tankōbon volumes have been released and an anime series by Sanzigen aired from October to December 2013. The same studio also produced two films based on the series, released in January and October 2015.

These are 29 keychains based on sigils of the warships present in the anime and manga (with or without mental models). They are Blue Steel, Fog Fleet sigil, Fog Fleet sigil as seen on the ships, I-401, Kirishima, Haruna, Takao, Hyuuga, Kongou, I-400, I-402, Maya, Hiei, Myoukou, Haguro, Nachi, Ashigara, Musashi, Yamato, Ise, Vampire, Repulse, Zuikaku, Lexington, Nagato and 4 others i still didn´t figured it out who they are.There is also a core (Kirishima´s core) as seen in the episode 4 (Assault on Yokosuka - Yokosuka Kyūshū - 横須賀急襲) of the anime, salvaged by Haruna after Iona's last Erosion Torpedo which had been concealed inside Mikasa's wreckage triggers a chain reaction, destroying both ships.