Natsuki's whole reason for bringing Kenji? She thinks this might be Sakae's last summer and wanted Sakae to not be worried about her and how she was doing and knew her seeming to have a fiance would help with that. She just wanted Granny Sakae to be happy.
When Natsuki loses the 49th round and doesn't have enough accounts to continue the game and all seems lost, a boy from Germany shows up to offer his account. Within seconds, people from around the globe offer their accounts so Natsuki can defeat Love Machine. According to Sakuma, it was about 13.837% of OZ's total subscribers, over 150 million accounts.
"Please protect our families."
Sakae's final conversation with Kenji before her death. What made it even more bittersweet is the fact that she had faith in him the whole time.
The scene where Natsuki asks Kenji to hold her and make "them" stop. Just as he's about to ask what she means, Natsuki extends her hand to him and begins to cry. The dam breaks, the moment he touches her hand. Also doubles as a Tear Jerker.
Even though Shota taking ice away from the super computer was a big mistake, it was still very sweet of him to do so because he wanted to keep Granny Sakae's corpse cool.
Seeing Wabisuke's reaction to Sakae's death was pretty touching. After Natsuki calls him with the news, he Drives Like Crazy back to the house, pulling up in a wrecked and dented car, screaming if it was true.
The reading of Sakae's will combines this with a good Tear Jerker.
When Wabisuke showed up, the first thing she asks him is, "Have you had anything to eat?" According to her will, the worst things are being hungry and being lonely. She's glad that he's back so she can fix both.
When the missile falls just short of its path, that moment when the entire family shields each other in one huge embrace.