Every time Setsuko Harmon holds her newborn granddaughter, it's like the pair are meeting for the first time all over again.

That's because 77-year-old Harmon was diagnosed with Alzheimer's disease eight years ago, and is reintroduced to her month-old granddaughter several times a day.

Harmon and her daughter, Christine Stone first made headlines, after Stone uploaded several videos to Youtube, where she constantly told her mother she was pregnant.

Stone said she originally recorded the videos for her family, but convinced her reluctant father to let her publish them online. To their surprise, the videos inspired hundreds of thousands of people from across the world.

"The original video I made so Sadie would be able to see how much her grandmother loved her and how excited she was for her to arrive," Stone said. "Originally, I filmed it just for us, because the likelihood of my mom still being around when my daughter is 18 is slim to none."

"I wanted to show people, yes, it's a terrible disease, but you can still find moments of joy through it," she added.

In June, Stone said it will be a bittersweet moment when Harmon finally meets her daughter.

"I expect her not to remember her, but I know when my mom meets my daughter she's going to get excited every single time," she previously told PEOPLE. "It's sad, but it's not sad, because she will be just as excited to meet her over and over again."

Four months later, Stone gave birth to a healthy baby girl, Sadie.

Stone said the arrival of her daughter has significantly improved Harmon's mood, adding that her mother instantly falls in love with Sadie everytime she "meets" her.  

"My mom loves her," Stone told TODAY. "She was here for Thanksgiving and she said, 'Why can't I take the baby? I want to take her home?' It's put some pep in her step."

"But her short term memory is gone. Every time I say, 'Meet your granddaughter, Sadie,' she'll forget whose baby it is again five minutes later. She gets so excited all over again," Stone added.

Harmon was born in Japan, but moved to the U.S. after marrying her husband, Bob Harmon more than 46 years ago. Despite her illness, she still recalls some aspects of her Japanese culture.

"She remembers the words to an old Japanese lullaby song called 'Donguri Korokoro' about an acorn and an eel, and sings it to Sadie," Stone said. "I only video the good moments, I don't video the bad moments - and there are plenty of bad moments."