101Leafy researched the games.
Finblade

Bonecraft adds an elemental effect. Shoots high-pressure water from its cutting edge.
| Class | Great Sword |
|---|---|
| Rarity | 2 |
| Attack | 480 |
| Water | 260 |
| Slots | 0 |
| Price | 2,150z |
Upgrades
| Upgraded from | Bone Slasher |
|---|---|
| Upgrades into | Plesioth Watersword |
Can also be made new at the smithy.
Upgrade tree from モンスターハンターポータブル 2nd G 公式ガイドブック (Enterbrain, 2008), page 680.
Materials
Cephalos Scale ×4, Springnight Carp ×2, Piscine Fang ×2, Monster Fluid ×3