With This Fist, A Miracle Kohaku confirms the capsule is buried under the citadel’s largest tree, protected by another concrete shell, which she cannot break open without alerting guards. Senku, having deduced Byakuya would preserve the capsule using concrete, decides to send Kohaku a silent bomb. By mixing diluted sulphuric acid with Anhydrite he creates expanding Plaster which, when inserted into holes in the concrete, forcibly expands and cracks the concrete open from the inside. Kohaku finds a glass bottle she accidentally breaks but sends the powder it contained to Senku on the toy cars. It turns out to be mostly gold dust, but Senku is able to find an entire test tube worth of pure platinum. Given platinum's rarity Senku realises Byakuya must have spent decades dredging rivers to collect it for him; confirmed by flashbacks that Byakuya continued obsessively collecting it until his death of extreme old age, while still dredging a river. His children and grandchildren would then seal the bottle in the Soyuz per his wishes. Senku is beyond grateful for Byakuya’s sacrifice and, determined not to waste it, gets to work producing the nitric acid for more revival fluid. Ibara finds the Soyuz and realises an enemy has infiltrated the citadel. Senku’s first goal is to rescue his petrified friends on the Perseus.