Aibō DS (相棒ＤＳ) is a video game adaptation of Aibō (translated as "Partners"), a popular Japanese cop drama TV seres. The game takes place sometime within the first six seasons of the show as players control the then titular protagonists, Ukyo Sugishita and Kaoru Kameyama. Aibō DS aided promotion for Kanshiki Yonezawa no Jikenbo, the series's first spin-off movie in 2009.
Short audio and video recordings of the series' actors, photo replications of sets, and looped versions of music from the show make the bulk of the game's viewing experience.
After the tutorial session, the two Special Mission Officers can take on three cases unique to the game:
- Afterglow - Talented artist Reiichi Misawa is found dead within his atelier which can only be locked from the inside. Misawa's body smells like varnish and he appears to have died from a head injury from a fallen wall adornment. The Tokyo police are ready to rule his death an accident, yet Ukyo questions the adornment's odd positioning in relation to the victim's body. The Special Mission Unit picks up from the rushed investigation to get to the truth.
- Heartstrings of Murder - Kaoru's wife, Miwako, recommends for the duo to visit Wakamatsu Manor, home to a famous school of traditional music. When they arrive, the school's founder is dead and her disciples are viewed as prime suspects. One of them, Aiko Onomichi, gives her alibi to the Special Mission Officers. She claims to be suffering from shock and cannot remember the incident well. Her appeal leads to Sugishita's invested interest in the case.
- Dying Wish - Ukyo and Kaoru attend a Rakugo performance and befriend the storyteller, Sadahiko Yoshikawa. The storyteller bonds with Ukyo due to their similar personality and hobbies. When they receive news of Sadahiko's death two months later, the Special Mission Unit attend his funeral and pay their respects to the Yoshikawa family. His family insists the father died from a hit-and-run accident, but their shaky testimonies and dismissive behavior are too suspicious for the duo to ignore.
Players have to finish each case in consecutive order. Any case can be replayed after the game is cleared.
The general gameflow and parts of its interface mirrors Tecmo's earlier DS Suspense series.
Drama Mode is the main story. Each case is split within narrative and investigative segments. Narrative phases introduce characters, highlight clues, and provide pieces of evidence which can be used to solve the case. The stories are linear and dialogue heavy. The player has to manually tap the touch screen for each text box.
Investigation segments allow players to review the information they have learned. The touch screen is used to talk to characters, look at objects, or move to another location. Players may be asked to select a specific text prompt while conversing with a character in order to proceed with the story. Information can be reviewed by touching the briefcase icon. Saving is done by tapping the pen and ink icon. Once enough hints are gathered, the player can use Ukyo Vision to find the decisive clue to locate the true suspect in each case.
When the Special Mission Officers are together during the investigation segments, the player can touch their logo silhouette (or the Partners icon) to be reminded of the current goal. Their banter mirrors the show and includes tidbits of extra characterization between the duo.
It is impossible to fail, so it is easy to complete each case through simple trial and error. Incorrect options only alter dialogue choices, and the game includes an auto solve option for players who fail the puzzles too many times.
Novelizations for five episodes from five different seasons are featured in this mode. These episodes are often cited to be among staff and/or fan favorites; they are also referenced in later seasons or made into movie adaptations of the show:
- Confession of the Mask: season 1, episode 8: first story about the modern day Jack the Ripper.
- Pill Eater: season 2, episode 18: murder which reveals two of Chief Inspector Haruki Okouchi's secrets.
- The Common Murderer: season 3, episode 10: aging victim who suffers from survivor's guilt comes clean about a murder case.
- Woman with No Luck: season 4, episode 19: Sachiko Tsukimoto tries to leave the country to escape her life of jinxes.
- Liar: season 5, episode 8: the suspect keeps lying about his crime.
Unlike Drama Mode, there are no voices or animations. Players can flip through the pages of each episode and listen to music mirroring the show. Backgrounds can be screenshots from a key scene within the episode or changed to permanent brick or wood wallpapers. SELECT button includes an option to hop to a specific part of the story for rereading.
Bonus mode collects data gathered from the other modes into an encyclopedia. Inside references and character relationships are explained for those unfamiliar with the show.
Two mini games are included. The first is a simple Simon Says game with coffee. Drain the Special Mission Unit's coffee pot by holding down the pen on the touch screen and do it without getting spotted by the pair. The other is a memory game with case evidence. Remember the correct sequence and repeat it fifteen times for a high score.