Yeo Hoe-hyun

Oracle Engineering and the second-generation tycoon

Cafe employee (Ep. 1)

Woo Dae-seong, a transfer student and good swimmer who falls in love with Sol-i

Jeong Eui-sung, a hacker who has great digital skills, especially in computers, mobile phones and CCTV.

Park Eun-ho

Park Jae-hyung

Son Jin

Young Lee Yoo-beom

Choi Young-soo (Kang soo's younger brother) (Episodes 17–18)

Na Ki-soon

Lee Seung-ho

Crown Prince Soonhwoe

Sungkyunkwan student