Akiba's Trip: Undead & Undressed is a 3D fighting brawler set in a modern day version of Japan's Akihabara district in Tokyo. It is the sequel to the 2011 PSP game Akiba's Trip. The protagonist is called Nanashi or 'Nameless', but this can be changed before starting the game. He is an otaku-type high school student who is on his way to a job interview. He does not remember what happens next, but he ends up strapped on an operating table where he is told that just like many others he has signed a contract with the Magaimono organization. This contract allowed them to turn him into a synthister, a vampire-like superhuman that feeds off other people's life energy. He needs to absorb the energy for Magaimono, but he is quickly rescued by a girl called Shizuku Tokikaze. She is a friendly synthister and her blood allows the protagonist to withstand his task and defend Akihabara instead.

He becomes a hunter to defeat the synthisters who prey on regular humans. Along with a band of freedom fighters Nanashi gets to roam the streets of Akihabara with over 100 shops modeled after the real life ones. Fights are done with brawling beat 'em up gameplay against one or more opponents in a small environment. Just like the protagonist himself the synthisters are sensitive to sunlight, so he needs to weaken the durability of their clothing with attacks until a part starts to blink and then there is an opportunity to tear off one or multiple parts of their clothing through a stripping mechanic, exposing them to sunlight which kills them. When multiple parts blink it is possible to perform chain strips. Rather than being a hentai title, the game presents the undressing in a quirky manner and does not contain full nudity. In the fighting system it is possible to attack using multiple stances and perform duo attacks with allies. Attacks are based on targeting the head and the upper and lower body. They can be strung together to form combos and there are many types of weapons, that can be upgraded multiple times, each with their own attacks, strengths and weaknesses. The character is also able to jump, avoid incoming attacks and counter blocks with special moves that break them.

Next to the fights a large amount of time is spent exploring the environment and completing missions to earn money. There are also many NPCs to talk to. Conversations often have dialogue trees and the answers not only affect the fights with synthisters, but also the relationships with the male and female cast of characters who can join or leave the protagonist's, with the option to pursue one of four love interests with their own endgame. A lot of communication is accessible through a smartphone, for instance to receive e-mails, check the Pitter social network, access the map or use the camera to take shots. Because of the large environment it is possible to fast travel between locations. The game contains many shops where items, weapons, clothing and food can be bought and sold. The character's main characteristics are based around an attack and defense rating, as well as a large amount of customization for weapons and different types of clothing items that influence his head and upper and lower body durability during fights.