The Peerless Mature Hitman Wants to Live Quietly With His Daughters is a Manga/Manhwa/Manhua in english 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

Harland Defense is an older man. He holds the title of the world’s one and only Risk Rarity 8 individual, and that’s not all: he’s also a peerless hit man who possesses extraordinary strength. He is employed by national governments and the big shots who run the world, and as soon as he receives his weapon from a girl known as “Mourning Dress,” he completes every job with the utmost degree of care and perfection. All he wants is to create a world free of crime. However, the so-called strongest hit man had one small weakness… There’s a group of peaceful girls with unfortunate circumstances living in the apartment building that Harland manages? A peerless older man with two sides: his ordinary life together with beautiful girls who have troubled pasts, and his life as a hit man! Presenting a brand-new colored comic series by Kazuma Kamachi, the author of “A Certain Magical Index” and “A Certain Scientific Railgun”!