Gilbert Kent (ギルバート・ケント,Girubāto Kento?) is Sakuya's illegitimate half-brother. He does not look Japanese due to his foreign facial features and his blonde curly hair, but Sakuya thinks they look "alike". After Nagi's grandfather announced a condition to inherit the Sanzenin fortune, Gilbert quickly begins to pursue the fortune, even going to the extent of begging for it.
Not only aiming to gain the Sanzenin fortune, he's also an Australian who entered the life saver training program at the beachside restaurant named LIFE in Heroes of the Sea Lifesavers.
Gilbert has blonde curly hair and blue eyes. He he is usually seen wearing a white suit.
Wanting to take the Sanzenin Inheritance
Gilbert is actually the first person to try and take the Sanzenin inheritance. When Hayate and Nagi were about to leave Mikado's castle, Gilbert attacked them out of nowhere. He demanded Nagi to cry and apologize to him, as this was the initial requirement in attaining the Sanzenin fortune. When Nagi refused he started to beg her to do it. Nagi immediately dismissed him making Gilbert resume his attack on Hayate saying that if he is able to harm Hayate, Nagi will surely cry and apologize. Unfortunately for Gilbert he was not strong enough and Hayate easily beat him.
He again tried to take the Sanzenin inheritance during the time Nagi sold Hayate off to Isumi. Nagi was feeling troubled about Hayate's feelings towards her when Gilbert appeared and proposed to test Hayate's love, but in truth his plan was to try various things to make Nagi cry. Gilbert suggested to feign a kidnapping and see if Hayate will come and rescue her. Nagi initially rejected the plan but Gilbert took advantage of Nagi's personality and started insulting her that she was a gutless weakling. Nagi was angered and she immediately accepted the plan to prove Gilbert wrong. Saki who was then taking care of Nagi was also dragged into this plan.
Making A Fake Kidnapping
They went to an underground cave to take the plan into action. Gilbert said that for this to be a true test of love the obstacle had to be great, Nagi then questioned his ability to fight Hayate. Gilbert admitted this and for that reason he brought a mecha with him that was created by Shiori. Sakuya who is Gilbert's illegitimate half-sister also came to the cave. It seems she heard of the false kidnapping and wanted to see Gilbert's plans.
It turns out that the mecha Gilbert was riding has the data from Eight : Nursing Robot, who bears a great hatred towards Nagi and Hayate, and the control chip Shiori made to prevent violence was not installed. The mecha started attacking Nagi and the rest when it was unable to locate Nagi's twin pony tails. Hayate arrived just in time to save Nagi and upon learning Gilbert was inside the mecha immediately held him responsible for the whole ordeal. Hayate easily took care of Gilbert and the mecha with a very powerful firearm.
In Mykonos to try to take the Sanzenin Inheritance
Gilbert again tried to gain the inheritance during Hayate and the other's trip to Mykonos. He confronted Hayate and Nagi but was immediately beaten up and ignored. He finally asked for a handicap to make his chances better. His conditions for the fight was to play a 2v2 beach volleyball game, and if he won the King's Jewel will be destroyed. To agree to these terms, he again insulted Nagi to provoke her. Naturally he succeeded and Nagi fell to his trap. Gilbert brought with him a robot specialized for volleyball as a partner and he took the liberty in choosing Hayate's partner. Out of the girls in the area: Maria, Izumi, Miki, Risa, Nagi and Hinagiku; Gilbert chose Hinagiku to be his partner, thinking she was the weakest.
Everything was going well for him because at that time Hinagiku intentionally held back in playing since she wanted to act weak in front of Hayate. However he made a mistake when he said that the reason he thought Hinagiku was weak was because she had a flat chest, he even further insulted her when he said she had malnourished breasts. The insults were enough to make Hinagiku serious, and with 1 hit of the volleyball destroyed Gilbert's partner. A shocked Gilbert called in his volleyball robot army and the game turned out to be a fight with a volleyball as a weapon. Gilbert and a single robot were left when he suddenly declares that Hinagiku was breaking a rule. According to him females are required to wear swimsuits when playing beach volleyball, Miki who wanted to see Hinagiku in a swimsuit agreed. Thinking that Hinagiku was too shy to continue playing in a swimsuit made Gilbert confident; however, an embarrassed and yet determined Hinagiku threw off her clothes to reveal her swimsuit. And with the final play of the game, Gilbert and his last robot were defeated.
For more information, see Heroes of the Sea Lifesavers.
Gilbert later becomes a famous life guard in Australia. He enters the training program at LIFE, just to beat Yamato Ikusabe in life saving. After he had saved Mitsumi from drowning, Gilbert starts flirting with her, causing Souya to angrily lash out at him. After a verbal argument, Gilbert challenges Souya to a competition. He then provokes him into accepting the challenge, after he had made an attempt to kiss Mitsumi on the check. During the competition the rules are explained to both of them, that the first one to swim to Mitsumi in the ocean is declared the winner. Gilbert attempts to cheat by using a jetpack, but ends up failing, as he takes up altitude and blasts off into the sky then plummets back into the ocean, landing on Souya knocking himself and Souya out ending the competition. After the competition, Gilbert regains consciousness, after having been saved by Ikusabe.