A narrow victory for Inter Turku over AC Oulu the previous evening had seen KuPS lose first place, and the reigning champions found the ideal time to earn a first league win in five games, as VPS picked up zero points for the second match running.
Two goals in six minutes put the visitors in control - former Inter Turku man Tommi Jyry struck his second of the season just before the 30-minute mark, before Petteri Pennanen's cross from the left was turned home with a stooping header from Joslyn Luyeye-Lutumba.
In the second half, the Vaasa side had 18 touches in the opposition box to KuPS' zero, yet they produced just one shot on goal for Johannes Kreidl so save, as the visitors' lead rarely looked threatened.
KuPS are top on goal difference, with theirs three goals better than Inter Turku's. VPS stay fifth, five points shy of the European places.
With survival already secured, Ilves are enjoying a great end to the season, as their comfortable away win in Turku was their third victory in a row and took them above TPS into eighth, while it's two defeats in a row and no wins in five for the home side.
Teemu Hytonen missed the chance to put Ilves in front when he had a penalty in the fourth minute saved by Elmo Henriksson, but when the visitors were awarded a second spot-kick midway through the half, Hytonen retained responsibility and made no mistake this time.
Ilves went 2-0 up midway through the second half when Elias Tamminen fired in off the post from the edge of the area, and Tamminen turned provider in added time, when he set the ball back for Stanislav Baranov to strike first time.