Operation Oppai (おっぱИ大作戦) by Akikana (あらきかなお) is the first chapter of the Overlord Official Comic A La Carte series.
Summary
Shalltear Bloodfallen yearns Ainz Ooal Gown as she stands close to him. Ainz Ooal Gown though finds her presence a distraction as she invading his personal space and sniffing him. Shalltear knows that Albedo has an advantage over her in the chest area, but is confident that she is better in other aspects.
However, she overhears the dark elf twins and Albedo talk about how Ainz had groped Albedo. Mare thinks that means Albedo will soon bare Ainz's child, though Aura states that decision should be up to Ainz. Her former surety is broken, Shalltear is determined to improve her breast size. To do this she does cupping, drinking milk, and mediating. Her efforts result in growing 1cm in bust. She rushes to tell Ainz, only to bump into Albedo chest. As she falls to the floor Shalltear realizes she can't win and decides to stick with her inner beauty.