Shadow 1 is the third Boss in Hero Story, and is fought with Sonic. The standard strat for this fight is to hit Shadow three times with storage, as he will not react to storage as if it can damage him. To hit shadow with storage, start holding B or X right before running into him. Move up-left to deliver the first hit, then adopt a hit-and-run strategy by creating distance and then going back in to deliver the other two hits. It is recommended to short-hop after landing each storage hit in order to get away faster and maintain control. Shadow can randomly perform a high jump after taking a hit, which will slow the fight down and force you to avoid taking a hit from him.
The fastest possible time with this strat that we know of is 11.29, assuming Shadow performs no high jumps. 11.3x is typically expected for clean fights.
In an IL setting, all that matters is getting a low in game time. Restarting the fight once will cause the timer to start later and it will effect Shadow's AI behavior, he will pause for a brief moment at the start of the fight before running forward. The first hit can be done faster by quickly doing one spindash cancel right at the start of the fight, then hitting shadow with storage, but this strategy is very difficult , as the camera isn't yet focused on sonic, and you must curve around to the right by a varying amount depending on when the spindash is released.. This strategy is not recommended for story runs, as it is high risk/ low reward, but it saves a notable amount of time in an IL setting.