Ben Tennyson and Julie Yamamoto

History
Julie first meets Ben as a crowd attendant to Ben's soccer game. She congratulates Ben on his win and tells him she has heard a lot about him.

Alien Force
She first meets him in the pilot episode of Ben 10 Returns: Part 1 as a crowd attendant to Ben's soccer game. She congratulates him on his win and seemed to have heard a lot about Ben.

In Pier Pressure, Ben first asks her out on a date. The date is interrupted when an alien named Ship, kidnaps Julie. During the rescue attempt, Julie finds ou about the Omnitrix and finds it cool instead of running away like Ben thought. They then decide to keep Ship and went home catching each other's hand.

In Good Copy, Bad Copy, she seems to be tuting Ben in Science, when they are going to have a test. She seems to be appreciating him that he was getting better day by day just to make him feel better. At the end of the episode, she seems to have get A, whereas ben seems to have get C+. He also tries to follow the way Julie opened her paper as he thought it might works for him too as it was Julie's method (although, according to him C+ was a great mark).

In Save the Last Dance, Julie and Ben, both seem to accept truly that they share the "boyfriend-girlfriend" title. Julie tries to help Ben by following his alien form wherever it went, just to make Ben feel better. She also openly accepted that if there was any problem in Ben's life, she would be always there for him. At the end of the episode, when Kevin teases Ben of being a "mother", Julie unsarcastically tells Ben that he made a great mommy. In this episode, the actual lovestory of Ben and Julie started to be gushing out through their veins by affections.

In Pet Project, Julie seemed to have felt Ben to be very honest, polite, kind and cute. Later, she started to get mad with Ben because she thought he didn't trust her. Although at the end it seemed that Julie took her worthy time revenge on Ben as Ship fell on Ben getting him afraid and hitting him. In this episode we got to see Ben get extremely protective about Julie and bearing no nonsense regarding her.

In War of the Worlds:Part 1, Ben seemed to be a little worried about Julie, as she did not have powers of her own and did not want anything to happen to her. Julie also shows a great concern of deal and affection for Ben. For instance, when Ben goes to the Highbreed home planet, Julie said: Be careful, Ben. At the end of War of the Worlds:Part 2, Ben and Julie get close to kissing, but decided against it, as Gwen, Kevin and Max were all looking on. Instead, Ben promises to walk Julie to the school and she gives him a loving smile and gets home by riding Ship.

In Vreedle, Vreedle, when Julie is being troubled by the Vreedle Brothers, Ben comes to her rescue and chases the Vreedle Brothers away. Then Ben and Kevin travelled half way across the galaxy only for Julie. This shows that Ben extremely loves her and cares about her. At the end, Julie too, said that he was ver concerned about her.

In Single-Handed Ben cut-off hand finds Julie for help, rather than going to Gwen and Kevin. This shows that Ben trusted Julie the most. Also when Gwen told that she could not locate Ben through her powers, Julie was almost broken down until Kevin told her that he was alright. When Ben came back to the Earth, Julie was very happy to see him alive and gives him a tight hug. She even tells that she would catch Ben's hand as a weapon for the situation (although Gwen found it romantic as she thought Julie meant marriage).

Ultimate Alien
The couple first appears in Fame, when first Ben goes to Julie's house in order to avoid the media and then takes Julie on a long drive in Ben's new car, the DX Mark 10. At the end of the episode Ben and Julie share their first kiss (although Julie kissed Ben on his cheek). The kiss also gave Ben a lot of confidence and he was utterly shocked at Julie kissing him. This episode also proved that the couple were at the peak of their relationship.

They reappeared in the episode Duped, when Ben makes three of himself so he can do whatever he wants. But Julie found, she was upset, angry and hurt because the original Ben chose to ge to the Sumo Slammers movie, leaving the immature Ben to watch Julie's match. In this episode Ben and Julie both admit publicly that they are a couple. Ben will soon make it up to her.

They reappeared inthe episode Hero Time, where everythings ging on well with Ben and Julie again and it is confirmed that their relationship is still going strong.