In the beginning Ash's relationship with Eco was shaky, with Eco stating that she is the master and often referring to Ash as a dog and not willing to make Ash Ark. Also because Ash originally did not want to be a breeder, which caused him to have doubts. After spending time together Ash has shown great care for Eco and being a breeder, while Eco had begun developing feelings for Ash, becoming jealous whenever he looks or spends time with another girl, especially Silvia.
After Mordred's attack and Ash rescuing Eco, she becomes more feminine and nervous around him, wanting a deeper relationship than master and dragon. When Eco got drunk she told Ash directly that she is in love with him and that she wants to have his child. After Ash told Eco that she can have children she becomes more confident in her advances towards Ash. (Volumes 8-9 of the Manga.)
When Oscar tricked Eco into getting drunk, the drunk Eco is calling out to Ash, then later crawling on him, licking him and telling him she loves him even more. (Volume 11 of the Manga.)
Ash has shown himself to be highly attracted to Eco's human form, and appears to be slowly falling in love. He has become somewhat nervous and hesitant in their relationship after learning that the Mother Dragon has a plan to use Ash to breed with Eco, and revive the Dragon Race.
This is Ash Blake's little sister whom Eco was originally intended to go but Ash's actions to save Silvia made the Mother Dragon chose him because her Breeder potential is greater than Ash, and she has the same ability as him to ride any Dragon as well but she is compensated later in the Light Novels when she is granted a Powerful Holy Maestro from the Avalon Line as a compensation for losing Eco.
Since their father left after her birth, Ash has been a father figure and admired older brother to Linda. While he cares for her like any brother, Linda has previously stated that she is in love, further describing her naive nature. She has shown to be somewhat protective of Ash when around other women.
In the beginning Ash and Silvia were at odds and had very negative opinions of each other. Ash thought of Silvia as a stuck up princess, while Silvia saw Ash as an out of control delinquent. This began to change after the dragon race when Silvia thanked him for helping her against some other players who were working against her. Silvia later began to develop feelings for Ash during her sisters visit where he inspired her to change herself for the better then gave har a piggyback ride, causing her to blush madly.
During their visit to the Mother Dragon Ash had regained his memories of his first visit , where he learned that he and Silvia had meet when they were 7, and that Ash had given Lancelot (who was meant to be his dragon instead of Eco) to Silvia after she was not chosen, to keep her dream of being a breeder alive. Later that day Silvia had found out that Ash was the boy she meet all those years ago. While talking to him about this she tells him how she wanted to meet him again for so long, then says that she won't hold back anymore. Without hesitation, she tells Ash that she loves him, then immediately runs up to him and kisses him passionately, right in front of Cosette and a very angry Eco.
After that the two became very awkward around each other, not knowing what to say, and Silvia becoming very shy when Ash talks to her or does something nice for her. When Oscar says the winner of the Student Councel Dragon Battle should be able to ask to receive anything they want Silvia requests that should she win, she wants Ash and her to be engaged. (Volume 10-11 of the Manga)
Ash is attracted to Silvia, with the definite potential of it becoming much something more, and there is a reason for this because Ash was the one that not only saved her but he gave away his Dragon who originally was Lancelot to keep her dreams alive because she wasn't chosen by the Mother Dragon but Ash nobly kept her Dream alive, and when she found out who he is she assaulted him with passionate kisses, because the person that she has always been in love was Ash the boy who saved her. (This happened in Volume 5 of the Light Novels/Volume 9 of the Manga.)
Ash finds Rebecca very attractive, but is also somewhat intimidated by her looks and force of personality. There also seemed to be falling in love like Echo.
Over time Rebecca has found herself to have been growing feeling for Ash, the first major example of this is when he stud up against Oscar, displaying a side of manliness, causing her body to heat up and shaking her calm and cool personality. Rebecca was also shown to be surprised when Ash made a deal with Oscar that he would have to give-up on Rebecca should he will, among other things.
During the Dragonar competition Rebecca had forged the match-ups so that she would face-off against Ash ignorer to train him for his fight against Oscar. After their match Ash brought a bouquet of flowers to bring to her in the hospital. However, on his way a Rebecca in a less then discrete disguise grabs him and bring him to the park. There Ash thanks Rebecca for everything she's done for him, then gives her the flowers. After which Rebecca tells him that she will be watching his match with Oscar and expects a good fight from him. Rebecca then goes back to the hospital, but not before kissing Ash right on the check, causing him to blush madly.
Ash seems a bit overwhelmed by Jessica's crush on him with good reason because she wants for his babies because she has a dream of becoming a Noble, and Ash being a Dragonar will keep her dreams alive, and she is very tenacious in getting what she wants. Over time Ash has been shown to tolerate Jessica, but has shown no romantic feeling to her or any signs of attraction.
(TBW) - To Be Written
Ash show great hostility towards Oscar after witnessing what "he" did to Silvia and other members of the student council after a battle.
Her identity and true gender as a girl was accidentally discovered by Ash later on Volume 6 and she gave him two choices are either get killed by her or become her second Queen, and becoming second Queen means having children with her because Rebecca is a girl and that is impossible.