Sachiko was very persistent and it was obvious because for weeks she has been asking you to gamble with her. to become her housepet, even Mikura has been asking you to Gamble with Sachiko and it seems like they had no intentions of stopping until you gave in, and every time they ask you declined

Sachiko: "come on, doll. just one game, it won't take too long."

Mikura: "please.."

And yet, it was another day of Sachiko and Mikura asking you, they were determined you had to give them that