From SG:

Title: Breaking the Habit
Fandom: Love Mode
Pairing: Takamiya Katsura/Sakashita Izumi; Aoe Reiji/Shirakawa Naoya
Categories: Established Relationship, Fluff
Length: Short
Warnings: None

Author on LJ: peroxide_fic 
Author Website: http://www.fanfiction.net/u/31057/

Review:
After attending health class, Naoya and Izumi realize exactly how dangerous their partners’ smoking habits are and decide, each in their own way, to do something about it.

What makes this fic so memorable is that Celeste manages to get everyone’s characterization spot on: Naoya, who still does his best not to "burden Aoe-san" in any way; Aoe, who will act gruffly, but will do anything to make his lover happy; Izumi, who despite all his protests cares for his lover deeply; and Takamiya, who will happily cater to Izumi’s every whim. Add some Naoya-Izumi friendship and a bit of the famous Izumi-Aoe rivalry and you have a delightfully amusing short story.

Breaking the Habit