Facing Wairarapa Bush, Whanganui lost 12-5 after they were virtually penalised out of the game, as well as being undone by some good play from Wairarapa's veterans Inia Katia and James Goodger.
Penalised three times in the opening 48 seconds, Whanganui were a man down when Te Tua Kemp was sent to the sinbin for two minutes.
Timoci Seruwalu ran over two tacklers and fed Ben Whale, but he could not hang on for what would have been the opening try.
The penalties kept mounting against Whanganui and Katia ran a switch play, attracting defenders, before the late cut pass saw Epeli Rayaqayaqa score for 7-0 after four minutes.
Te Rangatira Waitokia looked dangerous out wide but had two knock-on's ruled against him, the second one quite harsh as he regathered control but was ruled to have fumbled the ball into his tackler.
Whanganui were struck a further blow when key forward Tremaine Gilbert was helped off with an injury.
After halftime, Whanganui got on the attack from a Ben Whale dash, with Kemp and captain Dane Whale having a close crack at the line before Katia snatched the ball back and drew a relieving penalty for his team.
Another Seruwalu rampage over two defenders freed up Kameli Kuruyabaki, who sent the ball wide for Waitokia to close the gap to 7-5 with four minutes left.
A Katia half break with a good offload brought Wairarapa Bush back onto the attack and they controlled the ball in Whanganui's 22m for 14 phases, finally breaking through when Goodger powered forward and committed three tacklers, allowing Katia to sneak down an empty blindside from the ruck to score, 12-5 with 52 seconds left.
Again, Whanganui were penalised at the kickoff, although the defence forced the turnover to give them a Hail Mary chance from a 20m scrum.
Waitokia tried a desperate cross kick, but Goodger leapt up to bat it backwards and then regather, with Katia running the ball dead for fulltime.
It was a similar story in the six-team women's competition as the young Whanganui team lost their games to bigger unions.
At their first regional tournament, the Whanganui women were beaten 26-5 by Taranaki and 39-0 by Wellington in pool play, before losing their consolation playoff to Hawkes Bay 26-5.
Results
Men: Whanganui drew with Wellington 19-19; Whanganui lost to Horowhenua-Kapiti 19-0; Whanganui lost to Hawkes Bay 15-12. Consolation semifinal: Whanganui lost to Wairarapa Bush 12-5.
Women: Whanganui lost to Taranaki 26-5; Whanganui lost to Wellington 39-0. Consolation playoff: Whanganui lost to Hawkes Bay 26-5.