Epinel

A Burst 3 Wind Submachine Gun Nikke whose firepower depends on kill stacks and an area Burst.
She is rarely used in main slots for story, bosses, Raids, or Arena.
In boss fights where kills dry up and in meta firepower competition, her real performance is low.

Each kill builds a Super Rookie ATK stack, and using her Burst Skill damages all enemies; at full stacks the same damage lands once more. Landing the last bullet briefly raises her Crit Rate and Critical Damage.

Keep up rapid fire so the last bullet lands.
Kill mobs to build Super Rookie stacks, then use her Burst Skill.
Leave her on auto by default; in boss fights without kills, stacks do not fill and her Burst gains shrink.

There is little evidence of her being paired in the same squad in the recent meta.

Close-range accuracy matters for a Submachine Gun, so prioritize the Assault Cube. Cover sustained fire with the Bastion Cube and Resilience Cube. If Harmony Cube levels differ a lot, use the higher-level cube before the ranking.

To make use of her last-bullet crit bonus, prioritize Crit Rate and Critical Damage lines, and set Elemental Advantage damage and ATK later.

Unless she is a meta core unit, save skill books and only raise Super Rookie, Arachnid1, and SAFE 50-502 to 4 when you use her. Her stacks and double Burst hit are the core, so level all three skills together. Maxing to 10 gives little return for the investment.

She is rarely seen in top Solo Raid lineups. She is occasionally used for area firepower in mob sections of the Missilis Tower.

Killing mobs builds Super Rookie ATK stacks.
At full stacks, her Burst Skill damage hits all enemies twice.
Landing the last bullet raises her Crit Rate and Critical Damage.

When kills dry up, as in boss fights, her stacks and double Burst hit rarely cycle.
As a Submachine Gun, her rapid fire and crit bonus break off depending on range and accuracy.
She is rarely a main pick in the competition for the Burst 3 main firepower slot.