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Flint as he appears in Mother 3
|Appears in||Mother 3|
|First chapter||Chapter 1|
|Non-PSI ability||Brute Force|
In Mother 3
In Chapter 1, he first appears waiting for his family to come back from their vacation in the mountains; however, the forest is on fire, and Thomas demands that he helps with getting Lighter and Fuel out safely. Later he realizes that Hinawa and the kids have not returned, so he and the other residents of Tazmily Village begin a search to find them. Along the way he discovers a strand of Hinawa's dress on top of a cliff, so Wess sends Boney to bring Duster to assist him on scaling the cliff using wall staples. At the top they find Pigmasks then get attacked by a strange chimera, once defeated the Pigmasks flee, dropping a note about the Chimera project which Flint reads.
Unable to continue due to a section of a cliff having crumbled away, Flint and Duster return to the forest. Later he discovers Claus and Lucas have been found and are resting at a campfire by the river. However, it was discovered that Hinawa was killed by a Mecha Drago. Upon hearing the news, he is sent into a state of shock and depression. Several residents try to comfort him, however he begins lashing out on then using a stick, until Bronson knocks him unconscious with a log. He then dreams about the last time he saw Hinawa, before she is seen walking into the afterlife.
Flint then wakes up in Tazmily Jail, being the first person to have been put in. Bronson notes Flint's poor way of coping with his emotions, but still expresses his condolences reguarding the death of his wife. Claus arrives with an apple for Flint, saying he will get revenge on the Drago who killed his mother. Using the Hard File found in the apple core, Flint opens the cell to visit Hinawa's grave. At the grave, he finds out that Claus did indeed go to the mountains alone to avenge Hinawa, so taking the Drago dang Bronson made into a weapon, he heads out to Mt. Oriander to search for him. He arrives at Alec's house, where Alec tells him about a group of stange individuals who may know where Claus went. Alec joins Flint in his search for Claus, arriving at the house of the Magypsys, where Aeolia tells that they have given Claus a special ability to help him. Flint and Alec then climb the mountain to Drago Plateau in hopes of finding Claus. Instead, they find the Mecha Drago responsible for Hinawa's death. Once defeated, Flint attempts to kill the Drago as revenge, until the baby Drago comes to protect it. Alec tells Flint that killing the Drago won't fix anything, and instead make the baby suffer the same trauma which overcame Lucas, as such Flint decides to let the Drago live.
For the next three years, Flint's everyday life consisted of mourning for Hinawa and offering her flowers, and searching for Claus. He spends very little time with Lucas because of this, however in Chapter 7, he does give him his old Courage Badge as a good luck charm, albeit indirectly by telling Nippolyte to give it to Lucas the next time he sees him.
At the end of Chapter 8, Flint follows Lucas and his friends into the cave below New Pork City. He explains that there is something difficult Lucas needs to know, he continues on alone until reaching the strange dimension where the final Needle is located. When Lucas caught up to him, he reveals that the Masked Man is actually Claus, saying he had finally found Lucas's brother after all these years. At the plateau where the Needle stands, he tries to communicate with the Masked Man during the final battle, but is severely injured by the Masked Man's usage of PK Love Ω twice. After the battle, he asks Lucas to forgive his "hasty brother" and to pull the seventh and last needle.
Many fans have theorized that there is a connection between Flint and Ness, due in large part to Flint having possessed the Courage Badge. Shigesato Itoi explained that this was intentionally left open-ended, so that players who thought there was a connection "could go on thinking it if they liked." 
- Nindori.com interview with Shigesato Itoi, translated