Itsuka Tobitai Kazamidori

Asahiko, the reckless son of a long-established Western-style restaurant, spends his days lost in booze and women, letting the once-thriving business crumble.
In a bid to save the shop, Asahiko’s mother, the owner, calls in a business consultant, Komatsu, and the situation takes a dramatic turn.
Asahiko, uninterested in the restaurant’s future and willing to let it fail, clashes with Komatsu, who is determined to change the management strategy. But as they get to know each other’s pasts, their relationship begins to shift…!?

(Source: Shinshokan, translated)

Note: Includes one extra chapter.