2K-kun (2Kくん), also known as 2K-niisan (2k兄さん), is the OS-kun representing Windows 2000.
2K-kun is portrayed as a man in his late 20's to early 30's. He has blue eyes and short blue hair. Like 2K-tan, he wears glasses and has a cat ear-like headgear, albeit smaller than hers.
He wears a blue-grey formal suit with a Windows logo colored tie, and a dark blue cape over his suit.
He has a calm, rational and professional demeanor, and is highly skilled in both combat and office work. He tends to look after after his brothers and sisters with a sort of fatherly nature about him. However, alternative interpretations portrayed him as socially awkward or airheaded, and often struggling to read the room. Like 95-kun, 2K-kun also enjoys drinking and hanging out with other Futaba Channel characters.
2K-kun enjoys spending time with his family, despite his busy schedule at the office. He is often seen in the company of Me-kun and XP-kun, acting as the guardian to the former and a mentor figure to the latter. He sometimes gives advices to Homeo, which tend to be cryptic.
- He has a trick he only performs in banquets and parties, which is cutting a beer bottle with his hand from 10-15 meters away.
- 2K-kun met Sonata 13 years ago, and gave her a ring as a symbol of their friendship. Sonata mistook it for an engagement ring, and that caused an uproar in both the Windows Family and the Mac household.
- Windows 2000, page about the OS itself that also lists alternate personifications.