Frank is voiced by the late Daisuke Gouri (郷里 大輔, Gouri Daisuke) in Japanese, and by Chuck Cope in English.
Frank has blonde hair that is shaved to almost bald and green eyes. He is very muscular and having brutish pig-like features along with pointed ears (similar to Jack Mathers, making him a supposed relative).
Frank wears a green polo shirt with the logo of the Hamlin Battalion at the back, half-pants of regular Hamlin Battalion soldiers design with a black utility belt around his waist. Said utility belt is attached to his upper body by suspenders. He also wears a eye patch on his left eye, a green lieutenant hat and green gloves. As for equipment, there are numerous case boxes on his utility belt and there is a case box on his left pant leg. There is a power pack attached to his right pant leg which provides power to his railgun. He wears high tech acceleration device boots which allows him to move (includes jumping) at several times his normal speed (includes increasing jump height) but at the expense of consuming large amounts of energy (making it unsuitable for practical use by the military), limiting their usage to short periods of time and requiring to charge them once depleted, leaving Frank vulnerable while doing so. He has a device which prevents the Terror Bites from attacking him on his neck. As for weapons, he is armed with a railgun and uses Mosquito Terror Bites.
Frank led a group of soldiers occupying Dam #18 in California, United States, as part as a decoy operation to conceal the primary mission, which involved stealing the Terror Bites from the Biological Weapon Research Facility in Wyoming. Captain Rush eventually ran into Frank in the power facility of the dam, where Frank told him of the Hamlin Battalion's reasons for betraying the United States (which included an apparent lack of appreciation and recognition for their dangerous work). When Captain Rush said that the Hamlin Battalion is stealing Terror Bites for the purpose of making money, Frank counters by telling him that he is not comparable to the backstabbing traitor (Marcus Black). Soon after, Frank engages Captain Rush in battle. Despite Frank's effective usage of his acceleration device, his railgun and Terror Bites, he was gunned down, prompting him to trigger an explosion to destroy the dam and dies during the destruction.
|“||Aw, the lapdog thinks it can fight us?||„|
|~ Frank Mathers' first words to Captain Rush|
|“||Still haven't figured it out, huh? Do you have any idea how many reckless experiments we've been involved in? How many dangerous missions we've accomplished? But what do we get for breakin' our backs? Nothin'!! Top-secret unit? That just means that every single thing we do is covered up! And now! They're tryin' to make it look like we never even existed! Well, I'm not gonna take it any more!! We're gonna show the whole world, just what we can do!||„|
|~ Frank Mathers, explaining the rationality of the actions made by the Hamlin Battalion|
|“||Don't compare me to that back-stabbin' traitor (Marcus Black)! All he wanted was money... I'm gonna tear this country apart... and it's gonna feel good!||„|
|~ Frank Mathers, replying to Captain Rush who said that the Hamlin Battalion is selling weapons for money|
|“||...Hah hah... Now you're... finished... I did it, Jack (Jack Mathers)... Mission... Complete...||„|
|~ Frank Mathers' final words|