| Witness Genesect!|
| Number of Tretta
| Set number
| Release date
|| February 14, 2013
Witness Genesect! (Japanese: ゲノセクトを目撃せよ！) is the fourth Pokémon Tretta set. It features 48 Tretta.
Witness Genesect! features the Legendary Paleozoic Pokémon Genesect as a playable Pokémon for the first time in Pokémon Tretta, after appearing as a possible opponent in Challenge Cup events held prior to the set's release. Genesect is also one of two Pokémon to introduce the Bug type to Pokémon Tretta. The Legend-class Tretta for this set rounds off the Tao trio with Zekrom, with Kyurem and Reshiram included in the last two sets.
The Combo mechanic continues, though all Tretta featuring it have a icon as opposed to from the last set. Tretta with can still perform a Combo with each other, but not with those with . A new Form Change mechanic was also introduced, which allows the Pokémon depicted on Tretta with a icon to shift to an alternate form in Round 3 of Battle Mode. The starting form is present at the top of the illustration on each Tretta. After changing form, Pokémon retain their type and stats, but have access to a new move in place of the starting one.
For players with Tretta Reports, Witness Genesect! also replaces the previous roster of Bulbasaur, Charmander, and Squirtle as starting Partner Pokémon with the Generation IV starters Turtwig, Chimchar, and Piplup.
All regular Tretta are colored blue in this set. Beach once again replaces Cave in Search Mode, while the other locations have a spring theme.