The themes could include the journey of them coming to terms with their feelings for each other. Also, the idea of Ging's past and how it affects their relationship with Gon could be a major theme. There might also be themes about how their relationship impacts the world around them in the Hunter x Hunter universe.
I'm not sure specifically which Ging meets Gon in a 'boyfriend' context fanfictions are out there. You could try searching on popular fanfiction websites like Archive of Our Own or FanFiction.net. Just type in relevant keywords and browse through the results.
Shaflin was a character in the Ultraman series. He was called " That Lord " and was an extremely powerful villain. He was an alien who planned to destroy Ultraman and the Country of Light. Although the specific strength was not clearly described, according to the relevant discussions and comments, Shaflin was considered a very powerful existence. His strength was thought to be at least comparable to the King of Otto, and some even thought that his strength surpassed the other Ultraman. However, the specific strength assessment might differ according to different perspectives. Overall, Shaflin was considered a very powerful character in the Ultraman series.
Sandworms were extremely resilient, and even atomic bombs could not kill them. The only weakness of sandworms was pure water, which was highly toxic to them. Sandworms could produce spices, a by-product of their life cycle. Spices were highly respected for their medicinal and mystical properties, and were the most powerful currency in the entire universe. Consuming spices could strengthen some of the human body's functions to an unbelievable level, allowing the user to obtain a longer life span, greater vitality, and higher consciousness. In addition, sandworms also had territorial awareness. Usually, there would only be one sandworm in an area. Sandworms 'vitality and abilities made them an important factor in interstellar travel and human survival.
The Great Grandmasters of Qingyu referred to masters whose martial strength exceeded the level of Level Nine. They were the peak level that human beings could reach in this world. They were described as invincible existences who could fight against a small army by themselves. A great grandmaster had martial strength beyond the ninth grade and was one of the few peerless experts. However, there was an insurmountable gap between the strength of a Great Grandmaster and a Rank-9. The strength of a Rank-9 expert was far from that of a Great Grandmaster. Although great grandmasters were described as invincible existences in the years of Qing, they actually had their own limitations. The strength of a grandmaster was developed through the use of nuclear radiation. Although it could protect a region, it was not an invincible existence. To sum up, the Great Grandmaster in Qingyu was equivalent to a top-notch master above the ninth level. He was one of the very few peerless masters.
The great grandmasters in " Celebrating Years " were described as very powerful existences. Their strength could fight against 10,000 alone, and they could even easily defeat other experts. Among them, Wu Zhu was regarded as the strongest martial grandmaster. His combat power surpassed the other four martial grandmasters. Ye Liuyun, Ku He, and Sigu Jian were also very powerful Grandmasters, but they had all been defeated or seriously injured in their battle with Wu Zhu. As a mysterious Great Grandmaster hidden in the Royal Palace, the Qing Emperor also displayed great strength. However, the exact ranking of the martial grandmasters was not clear because each martial grandmaster had their own unique martial arts and cultivation. Therefore, it was impossible to accurately answer how strong a martial grandmaster was.
The shadow's strength was described in the " Celebrating Years " as being in the upper ninth-level, close to the Great Grandmaster level. He was the head of the Sixth Bureau of the Inspection Court and the chief envoy of the Inspection Court. He was respected as the number one assassin in the world and was proficient in all kinds of martial arts and assassination techniques. He was very powerful and was considered to be no weaker than a martial grandmaster. Thus, it could be said that the shadow had extremely high strength in the Qing Dynasty.
Xiao En's strength in Celebrating Years was that of a ninth-level master, and he had displayed the average level of ninth-level martial arts. He had taken poison for 20 years and was seriously injured, but he was still able to fight his opponent. The specific strength ranking was not mentioned, but Xiao En's strength was at the peak of the Rank-9. Therefore, it could be said that Sean was quite powerful.