Koritsuhai (Isolated Tiles) - Tiles Without Connections

What is Koritsuhai?

Koritsuhai (isolated tiles) are single tiles with no nearby connections in your hand. When all four adjacent tiles (±2 positions) are unavailable, that tile is isolated. These tiles have zero acceptance and should generally be discarded early.

For example, if 5m is isolated, it means 3m, 4m, 6m, and 7m are all unavailable (visible on table or used in melds).

Definition and Conditions

Isolated Tile Example

Hand: 234m 567p 789s 22E 5m

If 5m is isolated:
- 3m: Already used (in 234m)
- 4m: Already used (in 234m)
- 6m: All 4 visible
- 7m: All 4 visible
→ 5m is isolated, should cut

Handling Isolated Tiles

Priority Order

1. Completely isolated

   • Cut first
   • Zero acceptance

2. Semi-isolated

   • Only 1 adjacent usable
   • Cut next

3. Taatsu candidates

   • 2+ adjacents usable
   • Worth keeping

Exceptions

Isolated vs Taatsu

Value Comparison

【Higher Value】
Complete meld (triplet/sequence)
  ↑
Good taatsu (ryanmen/kanchan)
  ↑
Pair (head candidate)
  ↑
Semi-isolated (1 acceptance)
  ↑
Completely isolated (0 acceptance)
【Lower Value】

Tile Efficiency

Acceptance Count

Strategic Use

Early Game

• Cut actively
• Prioritize hand building
• Defense later

Mid Game

• Even isolated can be safe
• Cut dangerous isolates early
• Prioritize tenpai

Late Game

• Safe tile value highest
• Worth keeping isolated
• Defense first

Counting Method

Target: 5m

【Check items】
1. Is 3m usable? → No (4 visible)
2. Is 4m usable? → No (in hand already)
3. Is 6m usable? → No (4 visible)
4. Is 7m usable? → No (opponent called)

Conclusion: 5m is completely isolated

Common Mistakes

1. Confusion with honor tiles

   • Honor tiles aren’t called “koritsu”
   • Number tile concept

2. Incomplete isolation check

   • All 4 adjacent must be blocked
   • Even 1 usable = not isolated

3. Safe tile value

   • Isolated ≠ always useless
   • Defensive use exists

4. Dora handling

   • Dora worth keeping
   • Isolated still impacts hand

Related Terms

• Hai-kouritsu: Tile efficiency
• Taatsu: 2-tile meld candidate
• Ukihai: Floating tiles
• Fuyouhai: Unnecessary tiles
• Anzen-hai: Safe tiles

Summary

Koritsuhai are single tiles with no adjacent connections - all ±2 number tiles unavailable. With zero acceptance, they’re very inefficient for hand building and should generally be cut early. Beginners should learn the “all 4 adjacent unavailable = isolated” criterion and process these in early game. However, dora or safe tile situations are exceptions worth keeping. Understanding isolated tiles is fundamental to tile efficiency.