Dengeki Daisy(2007)

Dengeki Daisy

After orphan Teru Kurebayashi loses her beloved older brother, she finds solace in the messages she exchanges with DAISY, an enigmatic figure who can only be reached through the cell phone her brother left her. Meanwhile, mysterious Tasuku Kurosaki always seems to be around whenever Teru needs help. Could DAISY be a lot closer than Teru thinks?

One day at school, Teru accidentally breaks a window and agrees to pay for it by helping Kurosaki with chores around school. Kurosaki is an impossible taskmaster though, and he also seems to be hiding something important from Teru...

(Source: VIZ Media)

Included one-shot:
Volume 16: Hetakuso Cupid (The Hopeless Cupid)