Disclaimer: I own nothing.
6. obsession
Matsuoka Gou is many things. A friendly companion. A chatterbox. A good manager. Quick to anger. Leader-like. Supportive. Happy everything seems to be falling in place.
She's a nice person.
But she's not obsessed.
She's not, 'preoccupying or filling her mind [of someone] continually, intrusively, and to a troubling extent.'
Gou doesn't see anyone that way. Not her friends or strangers. Not her classmates or teachers. Not her family. Not her brother.
It's his muscles; she swears by it. It's not him. She obsesses over muscles.
And it's not her fault that Rin's muscles happen to be the best.