https://www.animelyrics.com/jpop/kaw...psimissing.htm
https://www.animelyrics.com/anime/index/psimissing.htm

I've already gone through and corrected the kanji and romaji (and typos in the footnotes)
This is a translation correction so please could you handle this @bluepenguin

I'll proceed in the order kanji, current translation, recommended translation, justification (just in case).

ここに生きるその訳も
Both reason to live here
Both the reason I'm alive here
[it would make more sense for it to be 住む if it meant live in that sense]


胸をチクリと刺す痛み
それを嘲笑(わら)う傍観者(しあわせなもの)達へ
背を向け行く
The pain pierces my chest
Everytime time happy people (bystanders) laugh (sneer)
Pointing at my size'
A prickling pain pierces my chest
I turn my back to those who are so happy (bystanders)
Who laugh (sneer) at that pain

[Looks like OP mistook チクリ for チンチクリン and also ignored the それ and the third line (which admittedly was originally romanised wrong)]


震えだす足が覚えてる確信に
幻想(ゆめ)だけじゃ守れない
頼らない力
今この手が知るから迷わない
My trembling legs start to remember... surely
I can't protect my dreams (illusions)
With this unreliable power
Now, knowing this hand, I won't lose my way
My legs, which begin to tremble, remember this... which becomes my certainty
With just dreams (illusions) I can't protect
It's an unreliable power-
Now, my hands have felt it, so I won't lose my way



百、千の必定も偶然が勝る
果てを見る瞳を凝らして飛び越える
怠慢な願いなど幾つもいらない
If a hundred, a thousand inevitable accidents happen
And I concentrate my eyes on watching the end... I'll go past them
I don't need countless careless wishes,
The number of coincidences outweigh a hundred or thousand certainties
I focus my eyes looking at the end... and jump over it
I don't need countless lazy wishes