Combat Mechanics

import { Table } from ‘@astrojs/starlight/components’;

Combat in Yomi no Sho is turn-based and deterministic given the RNG. Each fight is a series of rounds; in each round, the player and the enemy each take one action. The faster combatant acts first. The fight ends when one side’s HP reaches 0, or after 30 rounds (in which case the player loses — a timeout counts as a defeat).

This page documents the underlying math, so you can understand why your attacks hit for the numbers they do.

Turn order

Each round, the faster combatant acts first. If your SPD is higher than the enemy’s, you go first. If the enemy’s SPD is higher, they go first. Ties go to the player.

Some skills have a critBonus that adds to your crit chance for that skill only — but no skill modifies SPD or turn order. Speed is king.

The damage formula

When an attack lands (not dodged), the damage is calculated as:

base = max(1, attacker.ATK - defender.DEF × 0.5) × random(0.9, 1.1)
if crit: base = base × (critDmg / 100)         # critDmg base = 150%, so crit = ×1.5
if skill: base = base × skill.power             # multi-hit skills roll independently per hit
final = round(base)

Step by step:

Subtract defence. Take the attacker’s ATK and subtract half the defender’s DEF. The result is clamped to a minimum of 1 (you always deal at least 1 damage).
Apply variance. Multiply by a random number between 0.9 and 1.1. This is the ±10% swing that makes fights feel less mechanical.
Apply crit. If the attack crits (rolled against the attacker’s crit chance, plus any skill critBonus), multiply by 1.5. (Crit damage is fixed at 150% — there’s no gear or stat that increases it.)
Apply skill multiplier. If the attack is a skill, multiply by the skill’s power value. For multi-hit skills, this is applied per hit, with each hit rolling independently for crit and dodge.
Round. The final damage is rounded to an integer.

Worked example

A level 10 Samurai with 41 ATK using Iaido Strike (power 2.4) against a Tengu with 8 DEF:

base = max(1, 41 - 8 × 0.5) × random(0.9, 1.1)
     = max(1, 37) × ~1.0
     = 37

# No crit (assume 6% Samurai crit, didn't proc)
# Skill multiplier
37 × 2.4 = 88.8 → round to 89

# Final damage: ~89 (with ±10% swing, so anywhere from 80 to 98)

If the attack crits:

37 × 1.5 = 55.5
55.5 × 2.4 = 133.2 → round to 133

# Final damage: ~133 (with ±10% swing, so anywhere from 120 to 146)

So a crit roughly triples the damage of an Iaido Strike (1.5× from crit, plus the skill’s 2.4× multiplier compound multiplicatively).

Dodge

Every attack has a chance to be dodged. The dodge chance is calculated as:

dodge = min(25%, 5% + (defender.SPD - attacker.SPD) / 3 %)

Where the SPD difference only counts if the defender is faster than the attacker. So:

If defender SPD ≤ attacker SPD: dodge = 5% (base)
If defender SPD = attacker SPD + 3: dodge = 6%
If defender SPD = attacker SPD + 30: dodge = 15%
Dodge caps at 25%

A dodged attack deals 0 damage and is logged as “dodged” in the combat log. Multi-hit skills roll dodge independently per hit, so a 4-hit skill can have 2 hits land and 2 hits dodged.

Crit

Every attack has a chance to crit. The crit chance is:

crit = attacker.crit + skill.critBonus (if any)

Clamped to 0%–100%. A crit multiplies the damage by critDmg / 100, where critDmg is currently fixed at 150% for all classes. So a crit adds 50% damage.

Crit chance is rolled per hit for multi-hit skills, which is why multi-hit skills (Shikigami Barrage, Shadowstep Flurry, Kunai Storm) benefit so dramatically from crit-stacking. A 4-hit skill at 30% crit chance lands an average of 1.2 crits per use.

Enemy behaviour

Enemies have a simple AI: every round, they use a basic attack. There is a 10% chance the enemy is “furious” on any given round, in which case their attack deals ×1.5 damage.

Enemies do not use skills, do not heal, and do not have MP. Their only mechanic is the 10% “furious” chance, which is rolled per-round.

Player behaviour (auto-combat)

The player’s action each round is chosen by the auto-combat AI:

Pick the first skill in the enabled-skills list that is ready (cooldown = 0) and affordable (MP ≥ skill.mpCost).
If no skill is ready/affordable, use a basic attack (1.0× multiplier, no MP cost, no cooldown).

The “enabled-skills list” is ordered by when you unlocked the skills, with signature skills first. You can re-order or disable skills in the game UI (although the current implementation doesn’t expose this directly — see Skills for details).

The AI does not consider:

The enemy’s HP (it’ll use a nuke on a 1-HP enemy).
Its own HP (it won’t prioritise healing when low).
MP conservation (it’ll use skills until MP runs out, then fall back to basic attacks).

This is why manual skill management matters — the AI is dumb, and you can do better by toggling skills on/off based on the situation.

MP and cooldowns

Skills cost MP and have cooldowns (in turns). When you use a skill:

The MP cost is deducted immediately.
The cooldown is set to the skill’s cooldown value.
Each round, all cooldowns tick down by 1 (minimum 0).

So a skill with a 3-turn cooldown can be used every 4 rounds (use on round 1, cooldown counts down 3→2→1→0, usable again on round 4).

If you run out of MP, you can’t use skills. You fall back to basic attacks, which are 1.0× multiplier with no crit bonus. This is roughly 40% of your skill damage, which is why MP management is critical.

Combat log

Every fight produces a combat log, which is shown in the UI after the fight ends. Each entry looks like:

[Round 3] Player uses Iaido Strike (240% ATK) on Kodama
  Damage: 89 (crit: no, dodged: no)
  MP cost: 8

[Round 3] Enemy uses Basic Attack on Player
  Damage: 12 (crit: no, dodged: no)

[Round 4] Player uses Basic Attack on Kodama
  Damage: 18 (crit: no, dodged: no)
  (no skill ready — Moonlit Slash on cooldown, MP too low for Iaido Strike)

Reading the combat log is the best way to understand why you won or lost a fight. If you’re losing to a boss, check the log to see:

Are your skills firing? (If not, you’re out of MP — bring more MP gear.)
Are you critting? (If not, your crit chance is too low — invest in AGI or crit gear.)
Are you getting crit? (If yes, the enemy’s crit chance is high — invest in HP/DEF.)
Are you getting dodged? (If yes, the enemy’s SPD is too high — invest in SPD.)

The 30-round limit

Every fight has a hard cap of 30 rounds. If the fight isn’t over by round 30, the player loses (a timeout counts as a defeat, with no XP/gold/drops).

This rarely matters in normal play — most fights end in 5–10 rounds. But it can matter in boss fights against high-DEF enemies, where your damage per round is low. If you’re timing out, you need more ATK or a higher-multiplier skill.