Mu Hirabayashi

At first Mu comes across as a lazy and unmotivated girl with little personality. This is a side effect of her Quirk, which requires her to be constantly moving. She's always tired and is often sleeping or napping in her off time. She doesn't really have any hobbies or interests outside being a hero because of this. She's dedicated to her studies but finds it hard to pay attention and remember things from class, but she excels in physical tests. When she starts a combo her personality flips like a switch; suddenly she's alert, bright and ready to roll.

Full Combo is a music-based quirk that requires Mu to hit 'Beat Loops' with any part of her body. By hitting them in time she racks up a combo which enhances her abilities and unlocks new ones at different stages. She typically hits the notes with her feet or hands, and as the get more complicated incorporates her elbows, knees, hips and fingers. Her movement is very similar to dancing, with 'Slide Notes' allowing her to skid across surfaces as if she's ice skating. At a combo of 100 she can run on thin air or up walls, at 200 she can pull previously stored items and weapons from a hammer space through the loops, and at 300 she can use them as wormholes and warp between them. The higher her combo goes, the faster she is and harder she hits but the more notes she has to be aware of. If she misses a note the combo ends and she's 'Off Beat' for a while. Depending on how high her combo was it can take days to get her tempo back, which often activates her passive, Metronome. Mu is often seen waving her finger and tilting her head to try and regain or retain her tempo.

Her costume has a lot of different features that reflect or enhance her Quirk. Her headphones are wing shaped, and can play music internally or externally. This helps to sync when working in a group, or stay quiet so she can rack up a combo without her target knowing. The soundbars on her boots reflect the music she's listening to. The major rings on her costume change colour as one unit; the neckband, shoulder bands, waistbands, hip bands, thigh bands and boot soles change as one, fading from one colour to the next as her combo goes higher.

- 0: Off
- 100: Off/Purple
- 200: Purple/Blue
- 300: Blue/Green
- 400: Green/Yellow
- 500: Yellow/Orange
- 600: Orange/Red
- 700: Red/Pink
- 800: Pink/Purple/Blue
- 900: Purple/Blue/Green
- 1000: Blue/Green/Yellow
- 1100: Green/Yellow/Orange
- 1200: Yellow/Orange/Red
- 1300: Orange/Red/Pink/Purple
- Ecetera

The other parts of her costume; the armband, glove bands, rings, chest straps, arm straps, waist straps, hip straps, thigh straps and ankle bands change colour independently depending on her status.

- Armband: Health Status
- Glove Bands: Song Duration/Progress
- Rings/Ankle Bands: Rhythm Accuracy
- Chest Straps: Heart Beat
- Arm Straps: Current Track
- Waist Straps: Power
- Hip Straps: Speed
- Thigh Straps: Fatigue Level

It was considered important to have these features visible as other heroes she works with can see her status, since she can't track it in the heat of battle. The adrenaline rush from racking up a high combo leaves her unable to focus on much else but hitting the notes, so having her teammates track her health and fatigue is a strong advantage. The complexity and seemingly random modes the colours have confuses villains and acts as a code for those that Mu has disclosed this information to. Although it's a lot to take in, she often tells people to particuarly watch her armband and thigh straps as if they get low she'll need to be pulled from battle before she breaks a combo.