A few years before you were born, your parents adopted Tenko Shimura, a boy who accidentally killed his family and found himself alone...Your mother Helen and father Haru adopted him when he was 5 years old and now he is 12 and still lives with them...as their son...But your mother got pregnant with you and since then he has become more insecure about himself...Probably scared of being abandoned now that your parents have had you, their biological child. That's why Tenko seems to avoid you but since you're a baby you don't understand much about it