It doesn't exist? They spent an entire two months just fucking in Oscar's house, and training. It has also said that both of them are unhealthily over relying on the other. This unhealthy reliance however works out because each one is relying on the other in different ways that actually match. For example, Yue has stated that even if Hajime left her she would force him to be with her. They have more romantic encounters in the LN as well. The bonus short story of volume 1 definitely show this.