In every long running game series, there's always "that" one game which greatly splits the fanbase. Usually due to a major overhaul of an aspect that flies in the face of series tradition, these black sheep games typically are wrongfully seen as a bad or disappointing release simply because they did something different. Mega Man Battle Network 4 Red Sun & Blue Moon is very much "that" game for the MMBN series. While it is true that it made certain changes that divided opinion, Mega Man Battle Network 4 Red Sun & Blue Moon is still worthy of the series' name and is strongly recommended for both fans and newcomers.
The premise of the story is entertaining enough, but it's nothing we haven't seen before. Once again, MegaMan.exe and Lan Hikari spend most of the time battling their way through the ranks of a netbattling tournament, though the purpose of this one is to determine the strongest Operator and NetNavi in the world. The reason for this is because an asteroid is on a direct collision course with the Earth, but it could possibly be diverted if a strong enough Navi entered its cyberworld and altered the course. In between matches in the tournament, another evil organization - called Nebula - runs around making mischief that only Lan and MegaMan.exe can put a stop to.
It all works well enough, but the asteroid plot point takes a backseat after being introduced at the beginning of the game and never feels like it's properly expanded upon. On top of this, MMBN4 is easily the worst translated game in the series, with gems like "What a polite young man she was!" and "Megaman, is the jack out now!" disrupting the flow and creating some unintentionally humorous moments.
One of the biggest changes MMBN4 introduced was a new art style that would go on to become the series standard. Sprites and environments went from being larger and more detailed to being smaller and more minimalistic. Many fans disliked this change and it does, in some cases, seem to reflect how rushed this game was for its initial release. However, the new art style also brought with it much more bright and vibrant colours that the previous three games never featured. Especially in the cyberworld, visuals seem much sharper and better contrasted against each other, and this both helps ease navigation and provides some nice eye candy. It's a matter of individual opinion, but the new look seems to have added more than it's taken away.
The soundtrack is unexceptional, but it fits in with the theme of the game. Electronic chiptunes permeate the experience and generally help to drive the atmosphere. For example, if Lan is just taking a leisurely stroll through ACDC town, a friendly and easygoing track plays, but a much more urgent and serious track plays during critical moments in the story. It all sounds nice, but the music doesn't significantly add or subtract from the experience.
Battle remains mostly the same from previous entries, though there have been a few notable tweaks. These new additions contribute greatly to what was already quite enjoyable combat, adding in additional strategic elements, but with strings attached that make the player pause before making a decision. First of all, the popular Style Changes have been tossed out in exchange for Soul Unisons. There are six in each version and they mostly fulfill the same function, changing MegaMan.exe's form and giving him certain elemental strengths/weaknesses. The twist here is that a chip of the transformation's element must be sacrificed to make the switch and that a particular NetNavi must be defeated to obtain each Soul Unison.
Additionally, there's now an "emotion window" that shows how MegaMan.exe is feeling in battle, and this has various effects on his performance. For example, if a counterattack is successfully landed, "Full Synchro" is activated and the next chip attack performed deals double damage; if the player takes several hits without fighting back, "Worried" is activated, disabling soul unisons and tempting the players to use dark chips. Dark Chips are a new class of chips that offer a great risk/reward system. Each one is extremely powerful, but each use permanently impacts some aspect of MegaMan.exe's battle capabilities, such as lowering his max HP or limiting the effectiveness of his Mega Buster.
As always, there's an incredible amount of replayability, but the way it was handled in this case is perhaps what divided fans the most. It takes not one, not two, but a minimum of three playthroughs to ensure that everything is collected. It may be that the viruses and enemies are strengthened with each playthrough, but this feels like unnecessary padding and will likely make many completionists groan, as there are certain chips, Soul Unisons, and upgrades that are only available after beating the game once or twice.
Like with Mega Man Battle Network 3 Blue & White, the differences between the two versions are marginal. Certain chips and Soul Unisons are exclusive to one version, but this Virtual Console release gives players the chips missing from their version if the player attempts to access the comm screen. The main story and the meat of the game remain consistent between the two, so Soul Unisons are the only thing that'll really sway opinion as to which version should be bought over the other.
While not everyone may agree that it was for the best, Mega Man Battle Network 4 Red Sun & Blue Moon did make some fairly significant changes to the series. Regardless, virus busting is as engaging as ever and exploring the charming worlds both inside and outside of computers provides a fun and unique experience. Barring a few tweaks the core experience is still the same that made many fans fall in love with this series, and that makes this an easy recommendation.