This is the first of the basic movements for Yoshinkan Aikido: Tai no henko ("body changing motion") Ichi (#1). In English-speaking dojos we refer to it as "Cross-step body change". It combines the fundamental movement of a cross-step with two angle-changing hip motions. The motion bears a relationship to a spear thrusting motion in weapons training.
The Sokumen Irimi Nage (side step-in throw) technique is directly related to this basic movement, and follows it in the Kihon Dosa To Kanren Waza sequence.
Like the other basic movements, Tai No Henko Ichi has three forms: Solo, with Partner and with Sword. The solo version is shown in the first half of the video above.
The solo and with partner version of Tai No Henko Ichi are shown below as well: