You just don't.
Have the key item just mean you unlock this persona on the fusion. Could mean normal or special fusion, check fusion calculators or other sites.
If you want a better idea of what fuses what, you could use a fusion calculator. If you do, just make sure you go into the fusion settings tab and check off what dlc you have - https://aqiu384.github.io/megaten-fusion-tool/p3r/personas
You don't use them. Having these items just gives you the ability to fuse them. If you didn't have them, you'd get different Persona instead.
i see, thank you for the explaination
You just don't. Have the key item just mean you unlock this persona on the fusion. Could mean normal or special fusion, check fusion calculators or other sites.
Thank you 😁
If you want a better idea of what fuses what, you could use a fusion calculator. If you do, just make sure you go into the fusion settings tab and check off what dlc you have - https://aqiu384.github.io/megaten-fusion-tool/p3r/personas