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?

As Teru comes to terms with Kurosaki's past wrongdoings, Kurosaki searches for the culprit who is trying to resurrect the "Jack Frost" virus he created. But when he learns that Teru might be in danger, will he keep his promise to leave her alone, or will the two be reunited?