After learning iaijutsu and other techniques to combat firearms, Mitsurugi sought a sword appropriate for a new style of fighting. He finally
settled on Shishi-Oh (獅子王, lit. "Lion King"). An incredibly well-balanced Japanese sword, it is
Mitsurugi's preferred weapon.
During the intense training that he followed after his defeat in front of his lord, Mitsurugi became dissatisfied with his old katana Korefuji and replaced it with Shishi-Oh, a katana with a wider blade. With this blade Mitsurugi perfected many new sword fighting moves to defeat the rifle.
It is revealed that during the 17 year gap between Soulcalibur IV and Soulcalibur V, Mitsurugi lost Shishi-Oh to a female swordsman. She managed to shatter the katana, but Mitsurugi, seizing upon a chance, punched her in the stomach and took victory.
In Soulcalibur, Shishi-Oh was wielded by Arthur as well. This is because Arthur replaces Mitsurugi in countries that discouraged samurai imagery and references. When Arthur entered Soulcalibur III he wielded Gassan, one of Mitsurugi's optional weapons in Soulcalibur II.
In Soulcalibur V, Shishi-Oh is Mitsurugi's legendary weapon and is unlocked upon reaching Level 41.