Yumi, the protagonist of this story, started receiving unsolicited mail in her post box everyday.
Some kind of "love letters" (if you can even call them that) from a stalker.
Feeling grossed out and scared, she asks the young and handsome personal trainer at her gym for advice.

Like a gentleman, he escorts her home. At the entrance to her apartment, she thanks him...
Then... when attempting to close the door, he intervenes...
And divulges that HE is the secret admirer who has been sending her letters...