Weapon familiarity is a special stat that ranks your skill and adeptness for each weapon. Increasing the familiarity gauge through the ranks will unlock special heritage bonuses. The heritage bonuses can be transferred to new weapons at the Blacksmith forge — so there is no reason to discard useful weapons. Some of the best weapons have bad heritage upgrades, and some decent swords may have powerful heritage potential. That is why you should save and use money to increase your familiarity. Use the following methods to increase your familiarity:
1. Simply killing lots of enemies increases most of your familiarity, and it is most useful for the weapons you want to upgrade. Killing enemies, depending on their level, your level, and the weapon you are using, will always provide an upgrade to the weapon familiarity meter. Using a weapon is the best way to increase familiarity, and your primary weapons will easily rank up. To farm familiarity using this method, select the Yokai Realm arena side missions for a quick fight. You can also replay missions and use the Shrine to re-summon defeated enemies.
2. To quickly upgrade a weapon you do not use much in combat, use Whetstones to instantly increase the familiarity of your currently equipped weapon by +150. That is a good boost early and mid-game. They are also pretty cheap, and can be purchased from the Blacksmith. Purchase a lot of Whetstones and just keep using them to easily increase familiarity, especially with weaker or earlier game items that do not have a high maximum. You can then transfer the heritage to another weapon you do want to use —- just make sure the weapon has all the upgrades you want.
3. If you are using a weapon with a high familiarity boost, like bonus damage depending on your level, the Uchiko Powder is useful. Purchase a bunch from the Blacksmith and apply it to your sword before a tough fight to take advantage of the upgrade. Note: This only provides a temporary upgrade.
4. Magatama are common accessories you will find throughout the game, and often they will include weapon familiarity boosts built-in. Make sure to check each Magatama for stat buffs. These increases also stack, if you equip two at the same time, and more powerful Magatama will eventually unlock as you progress through the game. For better and more frequent drops, collect all the Kodama (green shrine spirits) in each region.