Now let's say hypothetically I was the impostor. How would I get from reactor to medbay in that timespan, from which we saw each other, till you found yellow dead. Also if I were the impostor hypothetically speaking, how would I have finished all my tasks.

You will never be Japanese. You have no ancestry, you have no citizenship, you have no skills that would make Japan ever want you. You are a shut-in self-hating white man twisted by delusions of mythical Japanese superiority and exposure to Japanese media into a disgusting mockery of nature’s perfection. All 'validation' you get from other people in this position couldn't be worse in making you believe that spending years of your life learning a globally useless language to a first-grader's level was a worthwhile use of your time, but one can't expect that an individual as pathetic as you will ever know the value of the youth you threw away in doing that. Actual Japanese are utterly repulsed by you. Thousands of years of linguistic evolution have allowed natives to identify frauds from mannerisms and vocabulary alone. Even if your written text of self-hatred and attention begging akin to a stray dog's somehow passes as normal (it won't), any Japanese person will immediately cut all ties when they hear the voice and accent of someone who is not only a basic Japanese speaker at best, but worth no more than garbage in skills, accomplishments, and likeability. You will never be happy. You wrench out a fake smile and laugh to yourself believing that watching a content creator that you understand 20% of at best is somehow superior than watching your own kind, as you project your disgusting traits onto your entire kind. However, deep inside you feel the depression creeping up like a weed, ready to crush you under the unbearable weight, and you know that. You know that all you do now is have an entirely new linguistic medium in which to be ignored, and not even the exotic trait of being foreign makes up for just how uninteresting of a person you are. Eventually it’ll be too much to bear - you’ll buy a rope, tie a noose, put it around your neck, and plunge into the cold abyss. Your parents will find you, heartbroken but relieved that they no longer have to live with the unbearable shame and disappointment. They’ll bury you with a headstone marked with your birth name, and every passerby for the rest of eternity will know a Western man is buried there. Your body will decay and go back to the dust, and all that will remain of your legacy is a skeleton that is unmistakably Caucasian. This is your fate. This is what you chose. There is no turning back. Hate yourself and apologize for being white to some Japanese entity that exists only in your mind while actual Japanese people put in effort to learn English for the valid reason of it being the global language.