Vietnam War Veterans in the World of Conan

Single female protagonist + other anime mixed in. The nightingale died, on the eve of a successful operation, in a foreign land. In order to avenge the nightingale, the flower grower launched a revenge against the black organization. During the operation, a group of scouts from the Vietnam battlefield were temporarily mobilized, and Chen Jixian was one of them. After Chen Jixian learned that Nightingale was his brother, although the two had never met, Chen Jixian decided to avenge his brother. For this reason, he went to Tokyo alone to seek revenge despite the dissuasion from his family. In the process, he met a group of characters with different personalities. And the black hands of the black organization are slowly approaching them. The showdown between the top killer emerging from the Vietnamese jungle and a half-century-old transnational criminal organization is about to begin.