Tsuyu and Habuko were both rather unpopular at their middle school, likely due to their amphibian/reptile-like characteristics, and unreadable facial expressions. Before meeting, Habuko would eerily watch Tsuyu, and eventually confront her, although this soon turned emotional. The girls quickly became friends upon hugging, and Habuko asked to call Tsuyu “Tsuyu-Chan”, which is a rather affectionate nickname.
After both girls splitter away, both couldn't see each other for a time physically. But they still had contact, so they often posted everything about their new life in a new school and their friends. Years later, they could recounter again after Aizawa made an announcement that there were going to be special guests for the Class 1-A practice exam. Habuko was still shy in front of the class, but after making visual contact with Asui, they recognized each other and both quickly hugged in signal of how much they missed each other. During the time the girls were changing themselves for the practice, both Asui and Habuko were holding hands as the other girls were watching and being a bit surprised that both went to the same school before. But for them, it felt a bit uneasy that Habuko was Tsuyu's friend, since she was a bit scary for the girls.
During the training, it's seen that the majority of the students that were participating were turned into zombies, since one of the guests had set his quirk free. Between the guests, Habuko was included, and when Tsuyu saw her turned into a zombie, she got sad while worrying about her. To avoid the zombies, the survivors had to slide the hill they were on so they could win a bit of time. But Tsuyu got distracted while sliding watching a Habuko as a zombie, and with this, she tripped with a rock of the hill, which made her fall down as she saw how the zombies were coming closer. Habuko then reaches Asui and surprisingly, she didn't bite Tsuyu, instead of that, she could recognize her best friend even if she was still a zombie. Asui was really happy about this, saying that they would always be best friends. But before she could finish her line, Aoyama (who was a zombie too), bit Asui from behind, turning her into a zombie. Both Habuko and Asui are shown enjoying their friendship as zombies together.
After the effects of the quirk wore out, the guests apologized from all the problems they had caused. While doig that, Habuko and Tsuyu were talking about how happy they were for seeing each other again. And even if they were zombies and were hurt, for them that was really fun. So they were happy again because they could be together, as the friends they were. And after that, both girls hugged while saying that they will work hard to become great pro heroes.
- Habuko – “I won't lose, Tsuyu-chan!”
- Tsuyu – “I'll give it my all too!”
- — The girls' interaction during the exam practice in the OVA - Training of the Dead
Though the ship it's not very big because of the short time screen that Habuko had in the Training of the Dead OVA, it sailed as result of the strong bond of friendship that both girls have with each other, though people prefer shipping them platonically rather than romantically. It rivals popular ships like TsuChako and TokoTsuyu. It is the most written for Habuko. Deku states it defies nature, which hints how strong their bond is.