The 4th Guard

From Fantasyshrine:

V.01 - Single Mind
S&D Securities – the 4th Guard gathers suave and intelligent professionals who are highly trained in combat. However, a reckless youth appears and is hell-bent on sticking to the intelligence manager, Taki Keiichi. Due to a previous assignment, Taki caught the attention of the yakuza and is now being pursued by this persistent rookie to join.

"I'm not going away until you either come with me or kill me!"

Amused by his earnest request, Taki offers for Yuuki to stay with him under the guise of his personal bodyguard. But Taki starts to develop a desire to oppress the ever obedient Yuuki…

V.02 - Second Wind
Kogami Shinobu is the number-one cool beauty of the Intelligence Department in the S&D Securities- the Fourth Guard, where suave and intelligent specialists gather in abundance. However, he doesn't seem to care for his partner, the laidback bodyguard Miharu "Shin" Shinnosuke’s pursuit. Why is it that Kogami stubbornly refuses to mix business with pleasure, as if he's scared of it? Then suddenly, Shin seems to have shifted his attention to the new charge he’s supposed to be protecting! What in the world will happen to their partnership–!?

V.03 - Third Party

V.04 - Four Card(s)

V.05 - Five Minutes

V.06 - Zero Hour

V.07 - Sixth Sigma

V.08 - Seventh Heaven

V.09 - Eight Knot(s)

V.10 - Nine Lives

V.11 - Ten Gong