Mutsu, second vessel of the Nagato-class battleships, stands among the elite "Big 7" warships, her legacy shadowed by a catastrophic magazine explosion within her third turret. This incident echoes through her dialogue as she cautions against recklessness with fire, openly acknowledges the tragedy in her library records, and emphasizes upgraded safety protocols to assuage lingering concerns. Her demeanor balances mischievous charm with vigilant responsibility. In her Kai Ni form, she adopts a nurturing "big sister" persona, cheerfully volunteering assistance—"Big sis will do it"—yet swiftly shifts to stern admonitions against dangerous behavior, particularly regarding fire hazards. Her dynamic with Nagato thrives on camaraderie; their synchronized battle lines during joint attacks underscore seamless coordination, such as commanding Nagato to advance in unison during fleet engagements. Visually, her design features maritime signal boom-inspired headgear, humorously likened by fans to snail antennae and earning her the playful moniker "Mutslug." While this trait remains a visual staple, official media treats it as a lighthearted quirk rather than a narrative element. Gameplay mechanics reinforce her role as a formidable battleship, with Kai Ni enhancements amplifying her firepower and enabling synergistic strikes contingent on specific fleet compositions. Promotional art and merchandise highlight her confident, coquettish flair, depicting her wielding heavy artillery with relaxed poise or blowing kisses, mirroring her in-game blend of boldness and levity. Historical authenticity grounds her character: post-remodel dialogue references anti-torpedo bulges and survivability upgrades, mirroring real-world naval engineering. Even her wedding line deftly deflects focus from her past vulnerabilities, humorously dismissing the turret incident to assert her unwavering presence.