Informer is a Manga/Manhwa/Manhua in english language, manhwa series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

‘Sejong’s secret weapon, Shadow Unit informer.’ Gwiyoung, called the Ghost’s Shadow, has been wandering around the battlefield since childhood. Vowing to get revenge, he decided to become a member of the nation’s first special forces as an informer.