Watashi no Tonari no Yandere-kun

"It seems like my kouhai Kishi-kun might be a stalker."

Rika, who works at a production company, is troubled by the presence of her kouhai, Kishi, who seems to be abnormally interested her. At the office, he's always staring at her behind her back. He notices even the smallest changes in her appearance, and on top of all that he also turns out to live next door?! He is so obsessed with Rika that he can't stop acting strangely, in ways that cross the line...! Yandere office love!

(Source: Peace!, translated)