Osare was the perfect choice for a full art of Tatsugiri thanks to their vibrant and colorful art style with bold black outlines that capture the Pokmons signature color palette
If your neighbor is doing the same thing, or the right cards arent flowing, then Boros wont work out, and it can be difficult to move from Boros into a different strategy
You can play less fair with Hope, too, by bringing in cards like Beacon of Immortality to potentially mill out the entire table in one move
Eevee and Mimikyu are obvious fits, and Alcremie from Brilliant Stars is one of the prettiest cozy cards around
Much like other boss monsters in the game, cards like "Solemn Warning" and "Black Horn of Heaven" can stop the Summoning of "Rainbow", while the "Kaijus" can effortlessly remove her from the field (assuming the Main Monster Zones aren't full)
Maybe it's a design decision.