40 x 40 Chikuwa Kaigi

Eiji and Koichi are such good friends their colleagues think they're dating. Since being roommates in the same dormitory some 20 years ago, they've gone through the same university, the same company, and living the married life under the same building. One day, they both find out that their wives want a divorce. While drunk and consoling each other, Eiji shares his troubles "down there" and it turns into a competition of who gets to make the other come first.

(Source: Otometika Shuppan, translated)