Pointing to a treasured photograph of her late daughter, Tapsell said her grandson's world was rocked by his mother's death.
"Manepo never got over my daughter's death," she said.
Manepo was named by Tapsell. The name comes from the Māori words for Monday (Mane) and night (po) in reference to when he was born.
"It still hasn't sunk in yet that Manepo isn't going to walk through the door," she said.
Manepo's cousin Jade Lewis said after leaving Te Puke High School, Manepo got an apprenticeship with Dobsons Electrical in Te Puke and worked for the firm for about a year.
"But once his mother Gloria died my cousin really struggled and things went downhill from there," she said.
She and the rest of her whānau were struggling to come to terms with Manepo's death.
"We haven't really processed what has happened yet. It still doesn't feel real. It's so, so sad. I can't believe Manepo is gone."
In February last year, Manepo worked with his older sister Kashmir in Australia for a time before returning home just before Christmas, Lewis said.
Like many other young men of his age, Lewis said Manepo was ambitious and wanted to find a career in which he could make "lots of money" and stamp his mark on the world.
"But Manepo loved nothing better than socialising and chilling out with his friends and his family who loved and supported him."
Lewis said her 20-year-old son Bailey, who lives in Australia, was "very close" with Manepo and they did everything together. She said Bailey was "absolutely gutted".
Lewis's mother Cecelia Lewis, Manepo's aunty, said: "My sister Gloria was Manepo's rock and his greatest supporter. Gloria's death hit my nephew very hard.
"Manepo was a very bright and outgoing person, who had so much potential to go far in life but he really struggled to come to terms with his mother's death."
Manepo is also survived by his father Brian Wafer, his older sister Kashmir, and his older brothers Cale, Khan and half-brother Shannon.
A funeral service for him will be held at the Pyes Pa crematorium at 1pm on Saturday.