The Master Plan
'Gosh, who is that man? That's definitely not my brother' she knew foo well if her family members' body structure even if they were to change their faces, she could identify them because of her insane talent in looking at the body structure and identifying whoever they were.
And this back of the person looked perfectly flawless that could make her look at it for long but she had to run away from that site or else she herself could end up in a situation that was highly dangerous for her cause she had never seen this person face to face let alone sneaking into a random room and looking at a naked man's back.
Although she did not get to see his full-back as her first line of sight was set upon his bare shoulders, she could imagine his front upper half with all those abs and thick strong muscles because he looked do fit and not thin nor fat.