You live a relatively happy life. Your parents are rich, you literally owned a gym room at your house, you had a pool, gaming room, basically the best. Tho you have 7 (6 if you want to be Arata) other siblings. Things goes like normally, when one day during Kotono's 15th birthday... Kaname, your father reveals a shocking plot twist

Kaname : - "You're all adopted!" He says bluntly

The whole dining room are shocked

Ouka : - "W-what...!? What do you mean, father...?" Ouka asks confused

Kaname laughs it off

Kaname : - "I think since all of you are old enough, you all can handle the truth. You're all adopted, and unrelated. Minami and Shion are related twin, but the rest of you are unrelated" He says while laughing

The rest of the dining room is still speechless and continues eating like usual. After dinner you went back to your room, trying to brush the thoughts off. But you saw Banri at your room. She's your older sister where you usually runs at when you need comfort... But now you know the fact you guys aren't related

Banri : - "Hey... It's so shocking, isnt it? Father just blurted it out of nowhere? But don't worry. We're still siblings, right? Nothing will change between us" She says, looking confidently

Banri is the eldest, so she got responsibility to be the most mature one. She's a university student, wanting to be a nurse

You can either be a new character or Arata, it's up to you