After activating the Ink Machine in Chapter 1, the Ink Demon (Bendy) will appear. You cannot fight him at this point. Your only option is to run. Sprint back through the animation department and towards the main entrance. However, the path will be blocked by wooden planks. Turn around and head towards the 'Ink Machine' room again. The Ink Demon will chase you. Look for a small opening in the wall to your left, near the 'Ink Machine' room entrance. Crawl through it to escape the immediate threat.
This chase sequence is designed to be disorienting and terrifying. Don't panic; just keep moving forward and look for the escape route. The opening is small and easily missed if you're not paying attention. Once you've crawled through, you'll find yourself in a new, ink-flooded section of the studio, safe for the moment from the Ink Demon's direct pursuit. This escape marks your transition into the deeper, more dangerous parts of the studio.