Nengara Nenbyaku Ansatsu Renka is a Manga/Manhwa/Manhua in (English/Raw) language, Action 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

The Haiboshi family's line of work is assassination. Takatori, their princess, picks up a boy named Raika who swore to dedicate everything.