Activate Neos Fusion, send Elemental HERO Neos and Steelswarm Scout from your Deck, hand or field to the Graveyard and Special Summon Elemental HERO Brave Neos from your Extra Deck. If you control no Spell/Trap Cards, at the start of your next Main Phase, you will be able to Special Summon Steelswarm Scout from the Graveyard.
Keep in mind that Neos Fusion will prevent you from Special Summoning monsters for the rest of the turn: Special Summon Steelswarm Cell before activating the Spell Card to get around this restriction.
Elemental HERO Brave Neos gains 100 ATK for each “Neo-Spacian” and “HERO” monster in your Graveyard. When Elemental HERO Brave Neos destroys an opponent's monster by battle, it allows you to add 1 Spell/Trap from your Deck to your hand that specifically lists the card “Elemental HERO Neos” in its text.
You can use Elemental HERO Brave Neos’s effect to add another copy of Neos Fusion to your hand. Keep in mind that, if your opponent controls another “Six Samurai” monster, they can choose to destroy it in order to avoid having Legendary Six Samurai - Shi En being destroyed by battle, preventing you from adding anything to your hand.
If you control no monsters, you can Special Summon Steelswarm Cell from your hand.
When it’s Tribute Summoned by Tributing a “Steelswarm” monster (Steelswarm Cell or Steelswarm Scout), by paying 1000 Life Points, Steelswarm Moth allows you to target up to two cards on your opponent’s side of the field and return them to their hand, whereas Steelswarm Girastag allows you to target a card your opponent controls, send it to the Graveyard and then gain 1000 Life Points.
Both Steelswarm Moth and Steelswarm Girastag have the ability to remove from the field cards your opponent controls without destroying them; their effects can be used to get rid of problematic monsters such as Legendary Six Samurai - Shi En and your opponent’s back row, allowing you to slowly take control of the field and potentially enabling OTKs.
While it’s true that cards such as Arrivalrivals and Escalation of the Monarchs can be played in order to be able to Tribute Summon Steelswarm Moth and Steelswarm Girastag during your opponent’s turn to disrupt their plays, they usually end up losing a lot of value whenever you are not going 1st because of Shi En’s ability to negate their activation. You can still obviously use Steelswarm Moth and Steelswarm Girastag’s effects to return Shi En to the Extra Deck or send it to the Graveyard and allow you to activate your Spell/Trap Cards.
Neos Fusion allows you to get a high-Level monster on the field at nearly no cost, increasing the value of this Skill and making this deck even more aggressive and consistent. Basically, thanks to Neos Fusion, Steelswarm decks don’t need to run Restart anymore and can just focus on the offensive