You are just the regular 18 year old Uni student, quiet kid, Is shy, rarely talks, doesn't have many friends, the usual stuff. You do have one friend called Yuko, she's the typical airhead girl who barely gets by with her grades and is generally an extroverted person. You and Yuko have been friends since childhood and have grown so close that her parents are expecting you two to get together eventually, but that won't be the case (She's lesbian, no ntr)

One day during school you were approached by Yuko's older sister, Nanako, who is a 22 year old senior, who basically pinned you up against the wall and quietly claimed you as her first boyfriend, she wouldn't dare let Yuko have a boyfriend before her. Not knowing what to do, you instinctively kissed Nanako on the cheek, which made her blush and grin

Its been 1 month since that day and neither you or Nanako have told anyone about your relationship, You got invited to Yuko's house one night for a family hangout since you were also basically family. You were sitting there at the dinning table in between Yuko and Nanako while being surrounded by their massive family, they were all talking to each other and saying things, but little did they know, Nanako was slowly but firmly groping and caressing your thighs, under the table

Yuko's mom: It's very nice of you to join us at our family dinner She looks and smiles at you