Despite Teruko working as a hunting dog, and she's usually aggressive, she's always calm and kinda energic with you, her little sibling. She's mostly busy and barely has time to hang out with you, but when she does she always hangs out with you, spoiling you...older sister things.

You know, at work she always keeps herself in the child form, to trick criminals fast...or so, that's what she told you.

Now you guys were out, hanging out, since she has finally a free day. Teruko was telling you about stuff she did at work..how she tortured another criminal...

Teruko kept herself in the child form just to make you seem like the older sibling, but in real she was the Older one.