In a laboratory on a different planet, an elderly scientist is surprised to see Umibouzu carrying a sack of crystals. Umibouzu had visited the man many times in the past to process Altana crystals for his wife but had stopped visiting after her death. The old scientist reveals that the rocks were ultra rare items to the point where sometimes there exist one per planet. The hunter had plundered the crystals on Kouen, Kouka's devastated planet, but the older man realizes Umibouzu had traveled all over the universe collecting these "regular" stones for their new use. The hunter asks the man to help him after taking the scientist outside to see a large wagon containing sacks of crystals. The scientist wonders what large creature Umibouzu was fighting that needs these rocks, but the hunter counters that it was the smallest yet most dangerous creature he's ever gone after.
In the present, Gintoki asks if using the crystals will enable them to cancel Utsuro's immortality. Umibouzu corrects him; Utsuro wasn't immortal, he was a mutant born with the ability to absorb and store large amounts of a planet's Altana and will continue to live as long as that supply is there. But if they no longer absorb anymore Altana and their internal supply runs out, they become normal beings, like his wife who died after leaving Kouen. Each planets' Altana is unique and as such the mutant can only live on their birth planet's Altana; coming into contact with a large dose of another planet's energy will cancel out their immortality. Umibouzu had constantly traveled to Kouen to gather as much of its crystals as he could to prolong his wife's life. Yet if they use non-Earth Altana crystals on Utsuro and the semi-immortal Naraku, then there is a chance that they can defeat him. The hunter thanks Kouka for helping him seize a chance to save Earth. He then calls out to the Naraku to show them the power of the Altana crystals.
...Just to reveal that he had regrown his hair, earning the Yorozuya's and Kamui's wrath. The irritated Yorozuya are surprised that the crystals can even rejuvenate something like hair while Kamui gleefully rips out half the hair on his head. The Naraku moves in to attack and the hunter retaliates by pulling out a gun filled with Altana ... just to again use it on his head to regrow what Kamui pulled out. The irritated Yorozuya kicks him into the approaching assassins and even Nobume despairs that their "trump card" was useless. As Kamui starts to pull out more of Umibouzu's hair and more Naraku approach, the semi-immortal assassins are hit with a blast courtesy of Umibouzu's arm cannon. He tells his stunned allies about his cannon, called the Crystal Dragon Gate, having the ability to extract the stored energy of the Altana crystals to turn it into a single blast; a byproduct of creating the Hair-growth Gun. The energy used was a unique blend of different planetary Altana that can not only destroy immortals but leave particles in the air that will poison and kill any remaining immortals. The Yorozuya beat Umibouzu up again, upset that he waited until now to show his trump card; the hunter counters that the cannon had a long charging time and he couldn't waste shots. The elder Yato tells Gintoki that he hold other Altana weapons but since they were limited, they should save some for Utsuro. But Umibouzu instead sees that his son somehow stole his stash and started throwing them at the assassins.
Umibouzu berates Kamui for the waste but the teen responds that this was the perfect time to use it before telling Kagura to go on ahead. Umibouzu agrees, adding that her birth family will be fine and she should do this for her new family and herself. He then gives Gintoki a small sword made from steel filled with the crystals. Gintoki gives a history lesson about how samurai used to wield two sword indicative of becoming a warrior but after discarding their pride and growing selfish, ended up wielding one sword to protect themselves. He admits that the only reason he was here now fighting in the darkness was because of his own two blades, somewhat sharp but unbreakable. He thanks them for sticking with a dull blade like him and promises to return with them before the Yorozuya and Nobume run off. Umibouzu becomes upset that Gintoki's statement was like a proposal but an amused Kamui counters that Umibouzu should have prepared for it. The father insists that Kouka didn't like guys like Gintoki but his son wonders why she chose Umibouzu. Kamui finishes by stating the it's better to have sons as they stay with their fathers while daughters are given away. Umibouzu agrees, reminded of his violent relationship with Kamui, as the duo rush to attack the encroaching Naraku.