Kinnikuman II Sei: Second Generation is a movie based on the sequel to Kinnikuman, the grandfather of many old fighting shonen people like to this day like Dragon Ball, Naruto and even One Piece.
However, this movie doesn't require any knowledge about the source material or its predecessor to be enjoyed as it is a simple action flick.
The Kinnikuman fights, or Ultimate Muscle for people outside of Japan, usually take place on rings and it is a wresting based fighting shonen. The characters fighting are referred to as Chojin which possess superhuman strength and abilities based on their designs. They come with unique strength and weaknesses as well as since fights take place in different kinds of rings, the environment usually plays a role as well.

In this movie, not much of these will be seen sadly. But the enemy does possess some unique techniques and a powerful armor protecting him from strong physical attacks.

The story involves with the main cast, the Justice Chojin who fight to protect Planet Earth, interacting with their fans. An Evil Chojin appears called The Cyborg and beats up most the cast and kidnaps the coach of the main character Mantaro Kinniku, also known as Kid Muscle.
Mantaro has to defeat The Cyborg and rescue his coach Meat before he falls to his doom.

A simple plot with a decent message put inside. We get a little of the mindset of various characters. The main character of the shows is obviously a selfish coward who tries to avoid getting involved at all cost, but a part of him when the situation calls for it he builds up courage and fights for those he cares about.
It is known for not taking it serious and being insanely goofy.

The movie is visually amazing as it takes place at the top of a tower with bright lights during the dark night. So visually the fighters pop out more than they normally do. And the threat illuminating Meat who stands at the edge of the power where a wrong move can lead to his death. Thus there is a time limit to the fight.

For Kinnikuman fans this movie might be missing some of what made the fights in the main story fun like unique strategies that seem simple but one will not come up with normally. The fights while looking impressive and great by fighting shonen standards, they feel basic compared to Kinnikuman fights. Meaning while the fights are good, they might not impress long time viewers or readers of the Kinnikuman franchise.

For non-Kinnikuman fans that want to give it a shot: If you are not bothered by the character designs and toilet humor like the MC pissing his pants from time to time, you might enjoy it. It is a side story of a continuation of a very good anime that set the standards for what many fighting shonen are known for.