As a pre-teen, Glenn was happy and a diligent person when he was trained by his older brother Dario in the art of swordsmanship and he is very close to his older brother. He also befriended Dario's friends Karsh and Riddel.
At the time of his older brother's death, Glenn overcomes his grief over his brother's loss and became a courageous, determined and brave swordsman as he joins up in Serge's party upon meeting him and at the same time, he and Riddel regularly visit Dario's grave.
When Glenn meets his older brother's dimensional counterpart at the Forbidden Island in Home World, he was overjoyed to see him alive and like Riddel, he does not want to hurt him when Dario was still possessed by the Masamune.
Once Dario was freed from Masamune's possession, Glenn proudly tells him of what he had accomplished as both a swordsman and a member of the Acacia Dragoons which indicates that Glenn finally surpasses both Dario and Karsh in both combat and swordsmanship.
He was born to Garai in 1000 A.D., and was raised in a log cabin with Dario next to Zappa's Smithy. During his youth, he made friends with the Acacia Dragoon gang, including Karsh and Riddel. He was known by his older compatriots for being hotheaded at times and also loving Viper Churros with a passion. Others recognized that he would be forced to grow up in the shadow of his brother; he frequently trained to match Dario's strength, and participated in the Viper Tournament of Swords. One year, he placed runner-up to Karsh's second and Dario's first. As he grew into an adolescent, Glenn continued to dream of becoming a strong Dragoon, even though Dario was killed in 1017 A.D. Riddel and Glenn often accompanied one another on trips to venerate Dario at his grave in Termina. By 1020 A.D., Glenn had become a formidable member of the junior Acacia Dragoon ranks; after Lynx befriended General Viper, he became wary of the visiting dignitary and began to suspect a plot. When Viper and the others retreated to Fort Dragonia, he stayed behind; Serge found him in Termina and convinced him to join his own voyage to the fort (alternatively, if Serge decided to find the Hydra Humour himself, Glenn went to the fort on his own accord). After the Dragon Tear shattered, Glenn returned to his former home in Termina (much to the occupying Porre soldiers' chagrin). He eventually rejoined Serge's party, wielding the holy Einlanzer. He soon meets Dario at the Forbidden Island in Home World (if he was in a party along with Riddel) and was overjoyed to see him alive until the arrival of Karsh and Radius. Glenn is also forced to battle his older brother who is now possessed by the Masamune and he is unable to kill him. After Dario was freed from the Masamune's possession and visited the ruins of the Viper Manor, Glenn proudly informs Dario of what he had accomplished while he thanked all of them upon seeing them alive in Another World as everyone in Home World have perished in the Dead Sea and he is only the sole survivor left in his former group.
While in Termina of Another World, he felt an impulse from the Einlanzer at Dario's grave there and took it up to wield both at once.
How to join
Glenn is recruited in a not-so-obvious way. When given the choice to help Kid, choose not to help her. When Macha takes Serge into Termina for a brief amount of time, go to the entrance where you first met Glenn. You will see him have a conversation with the flower lady at the entrance once more. Do as you please and when you feel the time is right, return to the boat where Macha is and Glenn will hop down from a ledge and request if he can join you.