Modern Yuki Judai (Fusion Teacher)

A very non-competitive Neos deck capable of kind of consistently Cosmo Locking the opponent and otherwise doing some HERO shenanigans.

I put in one level 4 E Hero of each attribute for lore reasons and because most of them are really good (Prisma admittedly is a bit too slow for the deck but we'll manage) so this is an actual E-Hero and Neo Spacian mish mash deck that genuinely works (making it a modern S2-4 Jaden deck)

As for the abseences of Air Hummingbird and Glow Moss: The Neos that shall not be named is too expensive to consider while the Glow Neos lines are just terrible... Storm Neos and Chaos Neos are pretty niche and very win more since if you manage to summon them their payoff won't be worth it anymore or the can seriously screw you over in the case of Chaos Neos (even though it looks awesome AF) so we're left with Nebula Neos and Magma Neos for the Triple Contacts who don't suck major balls compared to the other 2.

Aqua Neos and Marine Dolphin are some fun little additions to keep Neos Fusion and Instant Contact live while also being able to rip cards out of the opponent's hand.

Elemental HERO Core is just in here because he's my favourite HERO monster opposed to Jaden's fixation on Neos and he can float into a dead Shining Neos Wingman to lay down even more devastation, Absolute Zero to put some more pressure on the opponent to play around the board wipe, Infernal Rage to search/recycle for another Favorite Contact or any 1-Spacian Neos Fusion that might've died before which can then recycle itself into the Extra Deck.

Main Playmaker is of course A Hero Lives to get a combo started but there's some other less ideal lines we can also attempt to play through.

From just A Hero Lives we can grab Stratos who will in turn get Blazeman.

NS Blazeman to search Poly and use Blazeman and Stratos as material for Infernal Devicer.

Devicer searches Neos and a Neo Spacian (Maybe Aqua Dolphin or whatever you're missing in your opening hand for a Triple or Cosmo Neos).

Poly Devicer + Neos into Sunrise who will search Miracle Fusion.

Miracle Fuse Blazeman and Stratos/Neos into Flame Wingman - Infernal Rage who will search for Favorite Contact.

Set Favorite Contact which can summon a Hero Fusion Monster during your opponent's turn (probably Shining Neos Wingman).

As long as you can use Neos for what you want to summon I'd recommend banishing him for the Miracle Fusion since Favorite Contact also uses banished cards and puts them back into the deck. Of course if your hand has more things other than A Hero Lives your plays can be way more varied to include some more interesting HEROs like Solid/Liquid Soldier, Absolute Zero, Dark Law etc.

A really fun play of the deck is to use Liquid Soldier as a Fusion Material while having Cross Keeper in grave to essentially mulligan your hand by drawing 2 twice and putting one of them into the grave and one under the deck.

Since this is a Neos deck I didn't want to bother with staples because let's be honest: No way in hell this will ever be competitive but it's a fun list to learn/illustrate combo lines and different intricacies of the Fusion mechanic since we have regular Fusion from the hand/field (Poly), Tagging Out (Mask Change), Fusion from the grave (Miracle Fusion), Contact Fusing, Instant Fusing (Instant Contact), absolute Bullshit (Favorite Contact) and not Fusing at all but still summoning the appropriate monster (Neos Fusion) as well as Summoning Condition Ignorance (Now that I look at that list of features I get why people say this is a game for lawyers xD)