Kan. Stat. § 61-3406
If there are several plaintiffs properly joined and venue is determined by the residence of one of them, it shall be necessary that such plaintiff's claim is a substantial part of the action. If there are several defendants properly joined, venue of the action may be determined at the election of the plaintiff as to any one of the defendants against whom a substantial claim exists. If, before trial of an action on the merits is commenced, a party with reference to whom venue was determined ceases to be a party and venue would no longer be proper as to the remaining parties, on the application of any remaining party promptly made, the cause shall be transferred to a court of a county of proper jurisdiction and venue. If there is more than one such county, the transfer shall be to a county selected by the plaintiff.
K.S.A. 61-3406