The couple submitted their own respective messages to Los Angeles Superior Court Judge Charlaine Olmedo, in which they praised their That '70s Show costar, who was convicted on two counts of rape in May and ultimately sentenced to 30 years to life in prison.
Describing Masterson as "nothing but a positive influence on me," Kutcher said in court documents obtained by E! News that the actor was "an extraordinarily honest and intentional human being" who has never lied to him throughout their 25-year long friendship.
Kutcher, who is married to Kunis, thanked Masterson for being an "excellent" role model, adding, "I attribute not falling into the typical Hollywood life of drugs directly to Danny."
"Any time that we were to meet someone or interact with someone who was on drugs, or did drugs, he made it clear that that wouldn't be a good person to be friends with," Kutcher said. "And for me, that was an implication that if I were to do drugs, he wouldn't want to be friends with me, which is something I never would want to risk or jeopardize."
Kutcher, who also costarred with Masterson in The Ranch, recalled an incident at a pizza parlor as an example of Masterson's alleged ability to "set an extraordinary standard around how you treat other people."
"A belligerent man entered who is berating his girlfriend," he wrote. "We had never met or seen these people before, but Danny was the first person to jump to the defense of this girl. It was an incident he didn't have to get involved in but proactively chose to because the way this man was behaving was not right. He has always treated people with decency, equality, and generosity."
Kutcher ended his letter by acknowledging that while "judgement has been cast as guilty on two counts of rape by force and the victims have a great desire for justice," he expressed hope that his words would be taken into consideration, as well as the best interest of Masterson's 9-year-old daughter Fianna Francis, who he shares with wife Bijou Phillips.
"I do not believe he is an ongoing harm to society," Kutcher added, "and having his daughter raised without a present father would a tertiary injustice in and of itself."
On her behalf, Kunis said it felt "essential" to share "the remarkable influence Danny has had on my life and the lives of others." Similar to her husband, Kunis praised Masterson's commitment for "discouraging the use of drugs."
"His influence on me in this regard has been invaluable," she wrote. "In an industry where the pressures and temptations of substance use can be overwhelming, Danny played a pivotal role in guiding me away from such destructive paths. His dedication to avoiding all substances has inspired not only me but also countless others in our circle."
Moreover, Kunis praised Masterson as an "extraordinary" family man and devoted father.
"Witnessing his interactions with his daughter has been heartwarming and enlightening," Kunis continued. "He prioritizes his family, education, and happiness above all else, demonstrating his unwavering commitment to being a loving and responsible parent. As a father, he leads by example, instilling in her values that reflect integrity, compassion, and respect for others."
Other That '70s Show alums who wrote messages in support of Masterson included Debra Jo Rupp and Kurtwood Smith. The Ranch creator Jim Patterson and William Baldwin also wrote letters, as did his wife Bijou Phillips.
During Masterson's retrial, given that his first was declared a mistrial, prosecutors alleged the 45-year-old sexually assaulted three women between 2001 and 2003 at his Hollywood Hills home. Masterson, who pleaded not guilty and did not testify, was found guilty on two counts, with the jury unable to reach a verdict on the third count.
After the sentencing, Shawn Holley, one of Masterson's attorneys, maintained his innocence in a statement to E! News, adding that Masterson "did not commit the crimes for which he has been convicted and we—and the appellate lawyers—the best and the brightest in the country—are confident that these convictions will be overturned."