FC-消光劑 Leather Prep
If the leather is old, and you want to remove the manufactured finish (as indicated in the above photos), then the best way to prep the leather is with an Abrasive Pad. Wet the leather with the Prep and rub with the pad, the Prep will start to emulsify the old coating and the pad will loosen it. Wet a cloth with the prep and/or spray some prep onto the leather and wipe over with the cloth. This will remove any excess colour/finish still on the leather.
If the leather isn’t badly damaged it doesn’t require such drastic action. The leather can be simply wiped down with a cloth dampened in prep.
In both cases though, you should expect to see colour transferred onto the cloth, indicating the Prep is working.