Senku Ishigami, having recently learned from Luna that Dr. Xeno is a master of science, begins to recall his childhood, specifically the period when he was in elementary school and obsessed with scientific discovery. Young Senku, frustrated by the limitations of his own knowledge and resources, decides to email science facilities around the world with his questions, hoping for guidance. Most institutions ignore him, but Dr. Xeno, a NASA scientist, responds with detailed instructions and encouragement, empowering Senku to continue his experiments. This exchange marks the beginning of a mentor-student relationship, with Xeno genuinely enjoying the intellectual challenge posed by the young prodigy and Senku feeling inspired and validated by the attention of a real scientist.

As Senku grows older, he attempts to build his first rocket with his friend Taiju, but the project fails. Determined to succeed, Senku again reaches out to NASA, where most scientists dismiss his request for advanced information due to his age. However, Xeno once more responds, this time providing not just advice but also a list of materials Senku can use. Senku, with a mix of excitement and determination, borrows his father Byakuya's government-supplied credit card to gather the necessary components, showing both his resourcefulness and his deep desire to push the boundaries of what he can achieve.

Meanwhile, Xeno's own career at NASA is marked by frustration as his ambitious projects are repeatedly rejected, leaving him increasingly bitter and disillusioned with the scientific establishment. During a conversation with Byakuya at NASA, Xeno is presented with a hypothetical scenario: what would he do in a "stone world" where civilization has collapsed? Xeno responds without hesitation that he would rule with an iron fist, using science as a tool for control and eliminating anyone who opposed him. This moment reveals a fundamental ideological divide between Xeno and Senku, even as their scientific bond remains strong.

On the eve of the global petrification event, both Xeno and Senku independently analyze petrified swallows that have been discovered. Xeno, through careful observation, realizes that the swallows are not truly dead but are somehow maintaining consciousness within their stone shells. As the mysterious petrification wave approaches Earth, Xeno urgently orders his associates--Stanley, Luna, and others--to remain conscious at all costs, hoping that this will allow them to survive the coming catastrophe. Both Xeno and Senku, aware that corn will be crucial for their respective plans in a post-petrification world, strategize about a future trip to California to secure this vital resource. In the final moments before the wave hits, both scientists suddenly break free from their stone encasements, setting the stage for their eventual confrontation in the new world.

The episode juxtaposes these flashbacks with the present-day sniper standoff between Senku's group and Stanley, heightening the tension as the characters' past connections and current enmities come into sharp relief. Through these memories, Senku grapples with the complexity of his relationship with Xeno--once a mentor who nurtured his curiosity, now an adversary who stands in the way of his dream to revive civilization. The emotional weight of these revelations is palpable as Senku reflects on how their shared love of science has led them down such divergent paths.

The ending of Dr. STONE Season 4, Episode 7 "The Two Scientists" shows a flashback to Senku's childhood and his early relationship with Dr. Xeno, revealing how their mentor-student bond formed and how they worked together on scientific endeavors before the petrification event. The episode closes with the tension of the impending petrification and the beginning of the conflict between Senku and Dr. Xeno, setting the stage for the ongoing battle between their factions.

Expanded narrative of the ending scene by scene:

The episode concludes by shifting away from the present battlefield to a detailed flashback of Senku's childhood, where his passion for science first ignited. We see young Senku conducting humorous and ambitious experiments, highlighting his innate curiosity and brilliance. This segment emphasizes Senku's early motivations and his unique approach to science, which is both playful and rigorous.

Next, the narrative moves to Senku's relationship with Dr. Xeno, a NASA scientist who becomes his mentor. The episode portrays their collaboration as a meaningful alliance, with Dr. Xeno nurturing Senku's scientific mind and encouraging his pursuit of knowledge. This relationship is shown as complex and layered, with mutual respect but also underlying tension that foreshadows their future conflict.

The episode then depicts a secret meeting in the USA involving special forces like Stanley Snyder and Maya Biggs, alongside top scientists including Dr. Xeno. Here, they analyze the petrification stone, discovering that the petrification event is imminent and that the stone's properties resist degradation even under powerful radiation. Dr. Xeno reveals that the petrified swallows are conscious and suggests that staying awake might be key to surviving petrification.

Before more can be uncovered, the petrification event occurs: a green light envelops the Earth, turning all 7 billion people into stone statues. This moment is shown with dramatic intensity, marking the catastrophic turning point in the story.

The episode ends by highlighting the emotional and scientific stakes of this event, with glimpses of key characters' reactions and the beginning of the long struggle to restore humanity. Senku's bond with his father Byakuya is also touched upon, showing the personal side of his scientific quest.

Regarding the fate of main characters at this episode's end:

• Senku remains alive and determined, his childhood and mentorship with Dr. Xeno providing insight into his scientific resolve.

• Dr. Xeno is established as both a mentor and future antagonist, his scientific brilliance shadowed by his opposing goals.

• Stanley Snyder and Maya Biggs are introduced as key operatives involved in the petrification crisis.

• Byakuya Ishigami, Senku's father, is shown in flashbacks, reinforcing his influence on Senku's values and ambitions.

This episode serves as a crucial narrative bridge, deepening character backgrounds and setting up the ideological and scientific conflict that drives the series forward.

There is no specific information available in the search results regarding a post-credit scene for Dr. Stone Season 4, Episode 7, titled "The Two Scientists." However, the episode itself focuses on Senku's childhood and his relationship with Dr. Xeno, who was once his mentor but now serves as an adversary. The episode explores Senku's passion for science and his complicated past with Dr. Xeno, highlighting their divergent views on the use of science.

The main plot of the episode involves Senku's interactions with Luna, who is sent by Stanley to infiltrate the Kingdom of Science. Senku manages to extract information from her while also uncovering more about Dr. Xeno's past as a NASA scientist and his influence on Senku's early interest in rocket science. The episode blends humor, emotional depth, and scientific insights, setting the stage for future conflicts between Senku and Dr. Xeno.

Without specific details on a post-credit scene, it's unclear if there are any additional scenes after the credits roll. Typically, post-credit scenes in anime are used to tease upcoming events or provide additional context, but without direct information, it's impossible to describe any such scene for this episode.

Episode 7 reveals that Dr. Xeno was Senku's childhood mentor and a NASA scientist who first encouraged Senku's passion for rocket science. Their relationship was initially supportive, with Xeno providing Senku with scientific guidance and materials, but later diverged as Xeno adopted a more authoritarian view of science, leading to their current conflict.

The episode shows Senku and Dr. Xeno analyzing petrified swallows and realizing they are still alive and conscious. It also depicts Xeno ordering his team to remain conscious at all costs as the petrification wave hits the planet, setting the stage for the conflict between their factions.

Luna is sent by Stanley to infiltrate the Kingdom of Science and locate Taiju for assassination. Senku charms her to extract information, and during this interaction, they recreate ice cream, which delights Luna, revealing her motives and allegiances.

Senku and Francois recreate ice cream to charm Luna, and the episode flashes back to Senku's childhood rocket-building attempts, including his correspondence with NASA and Dr. Xeno. These moments emphasize the scientific ingenuity and mentorship central to the story.

The episode fleshes out Dr. Xeno by showing his bitterness from repeated project rejections at NASA, his authoritarian ideology about ruling with an iron fist in a stone world, and his complex relationship with Senku, blending personal history with his current antagonistic role.

Dr. STONE Season 4, Episode 7 ("The Two Scientists") is generally family friendly with only mild content that might be sensitive for children or very sensitive viewers. The episode focuses on character backstory and scientific themes without graphic violence or strong language.

Potentially objectionable or upsetting aspects include:

• Mild use of profanity (words like "shit," "dick," and "crap") but no strong language.
• Mild violence and emotional intensity, such as tense or dramatic moments, but no graphic gore or brutality.
• Some scenes may have a disaster movie vibe with suspense and tension, which could be unsettling for very young or sensitive children.
• Mild references to alcohol and medical use of antibiotics, but no drug abuse.

Overall, the episode is suitable for older children and teens, especially those comfortable with mild tension and scientific themes. Parents of younger or sensitive children may want to preview for the mild language and emotional intensity. There are no major spoilers or disturbing content revealed in this assessment.