The player character in the Tag Force games is the character controlled by the person playing the game. They choose the name of the character, control their actions and contents of his Deck.
The player enrolls at Duel Academy one month after the beginning of the school year during the month of May. As a transfer student, he is automatically placed in the Slifer Red dorm. The game is divided into three parts, each with different goals, all of which are ultimately accomplished through Dueling.
Whenever a conversation is prompted, you are given four options - to talk about "Duels", "The Academy", "Hobbies" or "Rumors". During each conversation one of the first three choices is randomly selected to harm affection, while the other two will improve it. This can be avoided by getting Pharaoh to follow you, should he be with you, all three choices will yield the best result. Affection can also be increased by giving the characters sandwiches that can be purchased at Duel Academy's card shop. Everyone has different tastes, though all seven characters love the Golden Eggwich. Affection is measured via a heart meter.
Once six hearts are obtained, the character will offer to become your partner. Filling the meter completely to seven hearts will result in the character gifting the player with cards that are hard to acquire elsewhere. One may attempt to get as many characters to six hearts as possible, and it is possible to get all seven to full before ending part one.
Each Sunday, Tag Duels are held at the Academy's Duel field. Of the seven characters, the one you have the best affection level with will be you partner for those Duels. Should multiple characters be equal, the one with the higher in-game number will partner with you. Due to this, should all characters be equal, the partner will be Jaden by default, as he is listed as Duelist #1. The SAL lab is unlocked as an visitable area, and may use the "Card Conversion" and "Rental" machines to expand their collection of cards.
At the end of July, the Tag Force tournament is held, and with it begins the game's second part.
When beginning this part, one may select any character with enough affection to be a partner for the duration of the playthrough. The player and their partner start with 10 GX Medals, and must bet them in Tag Duels with other Duelists. Up to five medals may be wagered per Duel, but the opponent decides the number. One may obtain the medals in singles or Tag Duels. One must acquire ninety GX Medals to make it the final round of the tournament, which takes place in a newly-built tower near Duel Academy that resembles Alcatraz. Defeating the four tag teams in the tower completes the part, and the tournament is won.
The game's third part is a conflict against the Shadow Riders. Each of the seven of them has brainwashed another character and they will function as the Riders' partners against the player and their partner. Should one of the characters involved in these Duels already be the player's partner, the Duel against them is simply skipped. Defeating all seven Shadow Riders forces the player into a Duel against their leader, Kagemaru. The player must Duel him twice in a row, in singles match. Defeating him ends the game. Once its been completed, one may select any of the game's Duelable characters as a partner after fulfilling certain conditions and several additional characters can also be unlocked.
In Yu-Gi-Oh! 5D's Tag Force 4, the player starts with a WATER Deck that is seemingly assembled from cards picked up from various locations around New Domino city, as shown in the prologue. They are free to change its contents and create more Decks.
In Yusei Fudo's Marker-less storyline (Tag Force 4), Rally mentions that the player has, at one point, owned a Duel Runner that is so loud and fast, it had scared a young girl by roaring past her at top speed.
In Luna's storyline (Tag Force 4), Luna berates the player character for trying to put on a shirt while still wearing his hat.
In her Tag Force 5 storyline, the player character is revealed to also able to hear duel spirits, though not as passively as Luna (as the duel spirit in question was specifically trying to call him).
In Tag Force 5, the various non-canon characters' photos reveal that the player character has chunky, nape-length dark brown hair.
Primo's storyline reveals that the player character is actually a Duel Robot from his time and is the prototype of the Ghosts. Which also explains why hasn't he aged between the GX timeline and the 5Ds timeline.