From the Burst damage calculation on the JP wiki:
Burst damage equation:
Burst damage={(Normal attack damage×(a+[Burst Up Effect])+b)/(# of hits)}×(# of hits)
More hits yield greater damage stability.
Burst Up effects:
Accessory OP
Union buff (1.5% per level)
Ability (like Countdown+)
Soul Kamihime
Rarity a b a b
N(small)
N(small)★
R(mid) 2.0 1500
R(mid)★ 2.5 1500
SR(large) 3.0 2000 3.0 2000
SR(large)★ 3.5 2000 3.5 2000
SSR(very large) 4.0 2500 4.5 2500
SSR(very large)★ 4.5 2500 5.0 2500
SSR(max) - - 5.5 3000
A star indicates a fully limit-breaked main-hand weapon.