Matoi Tsunetsuki holds student number 22 in class 2-F and demonstrates extreme romantic fixation through persistent stalking, currently targeting her teacher Nozomu Itoshiki after misinterpreting his remark as a love confession. She maintains unwavering devotion despite his rare acknowledgments and frequent dismay. Her invasive actions include unauthorized home entry via duplicate key, installing surveillance devices in his room, and initiating contact through calls or texts every five minutes. She constantly shadows Nozomu mere steps behind, emulating traditional Japanese spousal duties by adopting his mannerisms and attire—wearing a kimono and hakama identical to his. She monitors his communications, admitting to intercepting and discarding his mail before access. Intense jealousy surfaces toward anyone interacting with him.

Matoi’s personality and appearance shift to mirror her current obsession. She sports short black hair with blunt bangs, brown eyes, and frequently incorporates accessories like a neckerchief. Her name forms a deliberate pun on "tsune tsukimatoi" (always dangling after), reflecting her relentless pursuit.

In a spin-off narrative, she joins a reality survival game where she alternates personalities with Kafuka Fuura every few days. This inconsistency prompts her initial tribe to eliminate her early. Nozomu unexpectedly swaps places with her, transferring his advantage and enabling her continuation on a different tribe. She survives subsequent challenges before misplaced confidence triggers another vote-off, culminating in her 15th-place elimination after a final challenge.

No significant evolution occurs in her core stalking behaviors across appearances. Her background, family history, and motivations beyond obsessive fixation remain unexplored.