>>33549679In the Fate universe mana is transfered through bodily fluids.
This can be done via saliva, or more effectively, sexual fluids. This means that one of the most common ways for mages to replenish their mana stores is by drinking cum. This also serves as an effective way for poor mages to earn some extra money, as they can sell their bottled cum to other mages for a good amount of money.
In this scene, Chloe, who is a servant, requires mana to continue existing, so she initiated a mana transfer with Illya via kissing when her mana started to run out.
