Eiyuden Chronicle: Hundred Heroes

The highest level a weapon can reach is 15. This requires 54,500 baqua in total. This can be done at Douglas's smithy in the fortress town when it's maxed out

To max out the smithy:

* Upgrade castle to level 4, requiring 480 food, 60 pelts, 4 excellent lacquer, 2 legendary beast horns, 100 allies and 56560 funds
* Recruit Douglas (collect 10 iron ore after initiating his recruitment quest)
* Build or buy the following buildings/upgrades: Treasury Capacity 1, Smithy, Smithy Weapon Levels 1-3, requiring 4 iron ore, 150 stone, 22 orichalcum, 17 sacred tree chips and 13000 funds

While orichalcum and sacred tree chips can be gotten upon reaching Castle Harganthia (chips from the castle and orichalcum from Chelonian Golath (unlocked by Dijkstra's recruitment mission)), it's also possible to max out the Mission Guild and use tasks from there to gather the materials (spoilered to avoid taking up too much space here)