Wu Liuqi: Heibai Shuang Long

Mo Lang, a bad boy, and Bai Qi, his genius friend, lived a quiet life in a village in the distant country of Niuzhan. Until one day, a mysterious assassin from the country of Xuanwu appears, who completely subverts their lives, forcing the two youngsters to embark on an adventure that will change the world. The manhua is a prequel to the animated series Scissor Seven, chronicling events from before the original series.
(Source: Tencent, translated)