Why did Sewashi, Nobita's great-great-grandson, send Doraemon to the past? What was his original intention?

Okay, this question hits the nail on the head! This is the very starting point of the entire Doraemon story and something many people wonder about. Let me explain it in plain terms.

Sewashi's Original Goal in Sending Doraemon Back: To Change a Miserable Future

Simply put, Sewashi sent Doraemon back to fix his ancestor Nobita's "utterly disastrous" life, thereby improving his own future living conditions.

This might sound a bit selfish, but once you see Nobita's original fate, you might understand.

Nobita's "Original" Miserable Life

In the "original timeline" without Doraemon's intervention, Nobita's life path was like this:

Career Failure: As an adult, he started his own company. While celebrating with fireworks, he accidentally burned the company down, leaving him buried under a mountain of crushing debt.
Unhappy Marriage: He didn't marry his beloved Shizuka. Instead, he married Gian's sister – Jaiko. (This isn't meant to disparage Jaiko, but for Nobita, this wasn't the marriage he desired).
Burdening Descendants: Because of that massive debt, his descendants lived in poverty for generations, struggling to make ends meet.

Sewashi's Motivation: "I Don't Want to Be Poor Anymore!"

Sewashi, Nobita's great-great-grandson (grandson's grandson), is one of those unlucky descendants burdened by this debt.

In the 22nd century, his family is extremely poor. How poor? In the first chapter of the manga, it's mentioned that Sewashi's annual New Year's money is only 50 yen (roughly equivalent to a few dollars). In the highly advanced future, this is practically destitution.

So, Sewashi's motivation is very direct: He's had enough of being poor!

He believes the root of everything lies with his great-great-grandfather, Nobi Nobita. If he could go back in time and help Nobita change his failed life, making him more capable and happier, then the entire family's fate could be reversed. If Nobita's future improves, Sewashi's own future would also become prosperous, and he'd get more New Year's money.

The Core of the Plan: Changing Key Turning Points

Sewashi and Doraemon believed the key to changing Nobita's life was to help him become more motivated and capable, ultimately marrying his dream girl, Shizuka.

In their view, if this "key turning point" was changed, Nobita's life would take a completely different path, and the original tragic future of "bankruptcy and crushing debt" would naturally cease to exist.

Therefore, Doraemon's mission was to:

Take Care of Nobita: Help him with futuristic gadgets when he's bullied, fails exams, or faces difficulties.
Motivate Nobita: Encourage him to study hard, exercise, and develop his ability to solve problems independently.
Ultimate Goal: Make Nobita into someone capable of making Shizuka happy, thereby changing history.

To Summarize

So, Sewashi's original purpose in sending Doraemon back to the past boils down to these points:

Root Cause: Nobita's originally destined life was a failure, leading to generations of descendants (including Sewashi) living in poverty.
Direct Motivation: Sewashi wanted to escape poverty and change his own fate.
Specific Plan: Send the caretaker robot Doraemon to tutor and help Nobita, making him a better person so he could marry Shizuka and embark on a happy life path.

You could say the entire Doraemon story stems from a child's very simple yet deeply relatable wish: "I don't want to be poor anymore."

Hope this explanation helps!