Hiroto and Kazami have made a small but very important improvement in their relationship. However, the Build Divers and the Resistance are now overwhelmed by the attack of the mysterious Gunpla known as "Seltsam." The pendant that Muran entrusted to Hiroto and the others seems to become a key to turn the tide, but… Meanwhile, May begins gathering intelligence at Magee's bar.
...that this is our last remaining key
to turn the tide.
إن هذا مفتاحنا المتبقي الأخير لقلب الكفّة...
Er meinte, das wäre der letzte verbleibende
Schlüssel, das Blatt zu wenden!
Dijo que es la clave definitiva
para conseguir la victoria.
Ha dicho que es la clave definitiva
para conseguir la victoria.
C’est la clé qui nous mènera
à la victoire finale !
Ha detto anche che questa è l'ultima chiave 
che ci è rimasta per ribaltare la situazione.
Essa é a nossa última
chave para virar o jogo!
Сказал, что это наш последний ключ,
чтобы повернуть всё вспять!