[There's no real reason Faust should know this, unless he were to suggest Yona is a gossip who tells her weird older male acquaintances about her love life. He's not exactly close to Slaine. But Mephisto knows all about it, and he's not going to pass up the opportunity to tease him!]
[And really, who else would Slaine give a gift to??]
Slaine
Ah, a gift for Miss Yona, I take it?
[There's no real reason Faust should know this, unless he were to suggest Yona is a gossip who tells her weird older male acquaintances about her love life. He's not exactly close to Slaine. But Mephisto knows all about it, and he's not going to pass up the opportunity to tease him!]
[And really, who else would Slaine give a gift to??]