Illusomaginary Land

I used to dream a land frequentlyfrequently dream of an imaginary land.

The land that hurted me and motivated me to left itave and improve my own reality.life.

I still remember Shiro, one of my best friends, as well asbecause of his exceptional kindness.

Weeks, months, and years passed through andbut I couldn't forget the happiness of being there.

That's why, before leftaving, I promised Shiro I'd come back: ¶
- "Don't ever leave me alone again", he said.

- "Don't worry, I'll be back as soon as I get through this problem", I answered himreplied.

When I came back home, the beauty capturoverwhelmed me to the point that I would deletforsake almost everything to keep the fallacious,is mystical world.

After feeling delighted withenjoying its magnificence, I read Shiro's letters.

He missed me, and I did it as wellmissed him too.

I missed you so badly.

I used to dream of a land frequently.

TheA land that hurted me and motivated me to leftave it and improve my own reality.

However, a terrible event forced me to go away.

Weeks, months, and years passed through and I couldn't forget the happiness of being there.

Under a year:
"Weeks and months passed"

Over a year:
"Weeks, months, and years passed"

Of course, it wasn't the first time I wenthad gone away.

That's why, before (I left OR leaving), I promised Shiro I'd come back: ¶
- "Don't ever leave me alone again"," he said.

- "Don't worry, I'll be back as soon as I get throughover this problem"," I answered him.

answered OR replied

However, he didn't know that the reason Iit took years to come back was not only because there wasn't space left in my backpack, but also in my heart, too.

"there wasn't space left in my backpack"

Why did this stop you from coming back?

When I came back home, the beauty capturof it all captivated me to the point that I would delete almost everythingthrow it all away to keep themy fallacious, mystical world.

"the beauty" is ambiguous
"throw it all away" is an English idiom

After feelbeing delighted with its magnificence, I read Shiro's letters.

He missed me, and I did itmissed him as well.

I took a piece of paper and wrote the first thing that came to my mind: ¶
"It has been so long...

I used to dream of a land frequently.

The land that hurted me and motivated me to leftave it and improve my own reality.

to hurt past tense is hurt (not hurted)
to + infinitive

However, a terrible event forced me to goleave.

"leave" is better when you talk about going away from somewhere. "go" sounds more like you had to go there.

Weeks, months, and years passed through and I couldn't forget the happiness of being there.

When time "passes" using "through" is wrong. "pass through" is for a physical space. Plural of year is "years"
If you mean only one year then you have to say "a year"

Of course, it wasn't the first time I went awayleft.

"left" is better but your sentence is grammatically correct

That's why, before leftaving, I promised Shiro I'd come back: ¶
- "Don't ever leave me alone again", he said.

participle of "leave" is "leaving" not "lefting"

However, he didn't know that the reason I took years to come back was not only because there wasn't any space left in my backpack, but also in my heart.

The day had finally had arrived.

this flows better but i'm sorry i don't know how to explain why

When I came back home, [the beauty] captured me to the point that I would deletegive up almost everything to keep the fallacious,is mystical world.

what is "the beauty?"
i don't know what you mean by "delete" almost anything but if this is what you meant this is better
"Fallacious" is an odd choice because it means wrong, untrue, misleading, deceitful. it has a negative connotation

After feeling delighted withby its magnificence, I read Shiro's letters.

He missed me, and I did it as well.

I took a piece of paper and wrote the first thing that came to my mind: ¶
"It has been so long...

"to come to mind" is a set expression