Vandread The First Stage (season one) was immediately followed up by this OVA. This OVA, also known as Vandread Taidouhen Stage (The Movement Stage) was a recap of the first 13 episodes with additional footage. So, Vandread Taidouhen is not really a bridge between Vandread The First Stage and Vandread The Second Stage (season two). It was made to bring new viewers up to date as to what happened during the first season (Source: AniDB)

Kishimoto Kasumi, a 15-year-old girl, was supposed to live at her auntie's house in order to go to high school since April. However, when she moved to the house she was surprised with the fact that there were already four new male students living in the same house. To make the matter worse, that day while she was taking a bath, Takasugi Yusaku, one of those boys, came into the bath and saw her naked. This is how Kasumi's troublesome high school days started. (Source: AniDB)

The third season doesn`t have a particular story behind everything (like Valkyrie Ghost in the second season). It just tells 6 stories about the life of Kazuto & Co. with some additions: Raine and Chorus get a house on earth, the last three Valhalla princesses each get an episode, and in the last episode Kazuto and Valkyrie, who in the same episode managed to stay adult, >try< to marry again. (Source: ANN)

Milk-chan is a drooling, potty-mouthed baby who lives in an apartment with an obsolete robot named Tetsuko, a slug named Hanage, and an uncontrollable pet named Robodog. Whenever the President calls, Milk-chan and the gang rush to the scene to solve any type of problem - whether it's stopping a money counterfeiter hungry for Belgian waffles or counselling a school of drunk fish. At the same time, they have to avoid a nagging landlord, as they're six months behind their rent. (Source: ANN)