Name: First Aid
Range: Far
Dice Usage: Special
Attack Power:N/A
Tsukara Value: 35
Warrior
Affinity: N/A
Elemental Affinity: N/A
Benefit: Supplementary
Description: The user of this technique uses their Tsukara to heal another warrior. They are allowed to heal either themselves, an enemy, or an ally. Recover 100 HP of the target's HP each time this is used.

Does that mean that characters that already have that ability can't use it anymore unless they buy this?

No, because I'm pretty sure that no one else has this and has the same Tsukara cost or effect. If you made your own custom one, you're fine. If not, you can buy it. No more posting here. Unless you want to buy something.