Kilo

A Fire Code Machine Gun Burst 3 Defender Nikke.
She keeps a Nano Coating1 shield throughout battle, and her Burst Skill splits into damage to all enemies or a Max HP increase plus a Next shield's HP bonus, depending on whether Nano Coating1 is active.
She has no taunt, so she is more often used for shields and element-matched survival support than as a core tank, and her damage expectations are low.

At battle start, Nano Coating1, a shield based on final Max HP, stays on her. While Nano Coating1 is active, her Burst Skill deals ratio damage to all enemies by converting part of her final Max HP into ATK; when it is not active, she gets a brief Max HP increase. If Nano Coating1 is not active when she uses her Burst Skill, she reapplies Nano Coating1 and her Next shield's HP bonus builds in stages by use count. After a set number of normal attacks, she Restores shield HP while Nano Coating1 is active.

When Machine Gun overheating fills up, switch to reload to keep firing.
For AoE damage, use her Burst Skill while Nano Coating1 is active.
For the shield and HP bonus branch, use her Burst Skill when Nano Coating1 is not active.
Switch to manual only if you want to choose the branch yourself.

Keep Machine Gun fire going with reload and ammo refill, and manage overheat and reload cycles with extra Max Ammo. If Harmony Cube levels differ greatly, use the higher-level cube over the theoretical ranking.

Elemental Advantage damage and ATK are the baseline. As a Machine Gun, add Max Ammo. Cover DEF with gear and remaining lines.

Nano Coating1 and Self-Repair2 are her survival core, so raise both active skills first, and since her Burst branch damage and HP increase carry weight, max it last.

Used to hold out in long fights or deal AoE damage via her shield and Burst branches. She has no taunt, so she cannot lock enemy targeting onto herself.

Her Nano Coating1 shield lasts from battle start.
Her Burst Skill can switch between AoE damage and survival buffs depending on the situation.
After enough normal attacks, she Restores shield HP while Nano Coating1 is active.

You need to alternate between Machine Gun overheating and reloading.
She has no taunt, so she cannot draw enemy fire onto herself.
As a Defender, raw damage expectations are low.

Included in the Standard Recruit pool.