OVA episode 5: Ryoko reminiscing about watching Tenchi grow up from afar (sorta, her conscience was watching him while she was sealed away), especially when she could do nothing to comfort him during the sad moments (like his mother's death: little Tenchi is seen crying and sobbing for his mom, and an also saddened Ryoko can only watch).
Specially, two Washu centered scenes from the OAV. First, when she is petting Tenchi's little cousin Taro, who calls her "mama", and she says "no, little one... I'm not your mommy..." and hugs him. Second, when after the baby is taken back home, and Washu explains a part of her backstory to Tenchi and the girls - more specifically, about her husband and her estranged child. Yep, the second one goes into a Funny Moment as Washu cheers herself up by showing off her adult form, but right before that...
In episode 10 of the OVA, Tenchi finding his mother's kimono and just staring at it for several minutes while recalling what little he remembers about her.
When Tenchi is almost killed by Kagato in the OAV's with only Tsunami's intervention saving him. When that happens, Ayeka is terrified and screams horror, then Ryoko frees herself from the trap she's in and goes into space to see if he's still alive. She then finds his bloody scarf, cries a little, and screams "I will make you pay. YOU WILL PAY!!". Even if Tenchi did survive, it was one powerful moment.
In the next episode, after being beaten by Kagato, Ryoko cries and tells Tenchi she's sorry for failing him. Fortunately, Tenchi shows up to save her.
When Tenchi finds out that all the positive memories he attributes to his mother were actually just him superimposing Kiyone's image onto Rhea's actions, he realizes he hated his real mother enough that he effectively erased her from his mind, which makes him feel seriously guilty as a young adult.
OVA 5 ends on a quite a somber note as the Masaki family and everyone connected to them have to send Kenshi to Geminar in order to fulfil orders given to Rea, who was not ready to go back and do her mission. When her orders are removed once Kenshi is sent away, Rea breaks down into tears as she finally comes to grips that she sent her baby boy into a mysterious world.
