Form re-reading the first manga several times, I think I have discovered several rules in the manga I haven't seen anyone mention before. 1st is a initiative rule, where monsters with the highest level gets to attack first and the "battle phase" occurs for both players on both players turns. I require to actually test that theory, but from what I can tell by not attack or for each level higher, you can save up attacks to attack several monsters at once. 2nd there is possibly a rule similar to shogi and chess where there is an attacker and a defender, however this might be determined by who is currently on the offence and goes well with the next rule.
3rd is the forfeit of the battle phase to draw. Players will often do this throughout the first part of the manga, and not draw cards during their turn when they are on the offence. Defensive players may not have the same downside as to be able to play a counter attack. Attacks could still be allowed during the opponents turn and opponents turn attacks could maybe be the reason why we don't see direct attacks.
I still don't have all the data for this, but finding a very legit manga ruleset could be a lot of fun as compared to the real game where you have to know all the cards, I would much rather have a advanced rule format to learn, where the monsters are smaller pieces to this.
I also have been researching a lot about the first ever rules released by konami back in 1999 if anyone is interested in talking about that. Love!