After the victory over the Ryuzoji Clan and the Kyushu Campaign of Hideyoshi, Harunobu Arima gained stability and reached the height of glory. At the beginning of the Edo Period, however, his relationship with the Society of Jesus was compounded by an incident with a Portuguese ship. In addition, he was involved in a swindle by a shogunate official and as a result, Harunobu was taken to Kainokuni (Yamanashi Prefecture) where he was given the death penalty.
After that, Shimabara Peninsula was temporarily governed by Shigemasa Matsukura. He started building Shimabara Castle to replace Hinoe Castle, and this burdened the citizens with a huge amount of tax and labor. There was also an order from the bakufu (Japan’s feudal government or shogunate) to crack down on Christianity, which would lead to subsequent tragedy.
Applying the art of castle construction which he had learned during the Korean Invasion, Harunobu started building Hara Castle and it took about five years. Taking advantage of the location on a bluff surrounded by the ocean on three sides, a tremendously sturdy and beautiful castle was finally built. From the Edo Period, in addition to Nanban trading, Red Seal Ship trading (trading by ships with a shogunal license for foreign trade) began and he gained much more wealth. Furthermore, his son, Naozumi, was married to a great-granddaughter of Ieyasu Tokugawa, and from all of these advantages, Arima’s territory became stable and prosperous.
However, in 1608, an incident occurred. Harunobu’s Red Seal Ship and a Portuguese ship had a battle in Macao, and many Japanese were injured or killed. Harunobu asked Ieyasu for permission to retaliate and he attacked and sank a Portuguese ship outside the harbor of Nagasaki. After that, no more Portuguese ships arrived in the port of Kuchinotsu. Again, the relationship between the Society of Jesus and the Nanban trade, which had been indivisible, deteriorated. What is worse, this matter developed into a major catastrophe through which Harunobu would bring ruin upon himself.
After hearing about the successful retaliation against a Portuguese ship, Ieyasu Tokugawa praised Harunobu. However, a bakufu superintendent officer, Daihachi Okamoto took advantage of Harunobu’s situation. He told Harunobu, “As a reward for this attack, I will see to it that you get back the land that was once the Arima Clan’s.” Harunobu desperately wanted to get back the territory he had lost in the war against the Ryuzoji Clan, and for this reason, he believed Daihachi. He asked Harunobu for money and also gave him a fake red seal license, leading himself to yet another breach of trust.
When Ieyasu heard about this, Daihachi Okamoto was captured and burned alive at the stake. Harunobu was condemned for trying to get his former territory back, and was exiled to Kainokuni (Yamanashi Prefecture). Since both of them were Christians, this incident became one of the reasons to intensify the persecution of Christians all over Japan. Later on, Harunobu was given the death penalty; however, because suicide was forbidden in Christianity, he refused to commit seppuku (suicide by disembowelment). Instead, he made his retainer decapitate him while his wife and family watched. He kept his faith until the very end. It was 1612 when Harunobu’s life of 45 years came to a close.
Through this incident, Ieyasu felt how perilous Christianity was, and it resulted in promulgation of “Keicho-no-Kinkyorei”, a strict prohibition order against Christianity. Christian mission work had already been under a ban, but the bakufu had never directly persecuted believers. However, the new order pressured not only the samurai but also the common people to conversion. It was so strict that punishment was given to those who refused.
The son of Harunobu, Naozumi Arima, was a retainer of Ieyasu. Therefore, even though his father was given the death penalty, he was still allowed to succeed his father as the head of the family as well as inherit his territory. Soon after the succession, he turned away from Christianity and making a complete reversal, started to persecute Christians. He expelled missionaries and ordered the destruction of churches. The common people were also pressured to renounce their religious beliefs, however, there was a strongly-rooted Christian organization called Confraria, which made it difficult for him to eliminate Christians. He was worried that the bakufu might become skeptical of him, and therefore Naozumi was unrelenting in his persecution of Christians. He even killed his half brothers who were the children of his father and his second wife. However, his conscience was bothered by his actions, and eventually he could no longer stand his situation. Naozumi asked the bakufu for a transfer, and in 1614, he was placed in Nobeoka, Hyuga (Miyazaki Prefecture). At this time, many of his retainers left their positions as samurai and decided to stay and become farmers. They didn’t renounce their faith; they chose to stay on the Shimabara Peninsula.
To replace Naozumi, a daimyo, Shigemasa Matsukura, came to the Shimabara Peninsula. He is a person whom the missionaries would later call “Devil”. In 1618, he followed the order of Ikkoku–Ichijo–Rei (one castle in one feudal lord’s domain), and started to take down Hinoe Castle and Hara Castle while starting construction of Shimabara Castle. The building stones used to form the stone walls of Shimabara Castle were carried out from Hinoe and Hara Castles by the local citizens. Thus, it took approximately seven years, as well as a huge amount of tax and labor from the local citizens to finish building the very large and luxurious Shimabara Castle, which was far beyond what Shigemasa deserved.
Additionally, Shigemasa offered workforce for the renovation of Edo Castle, to show his loyalty for the bakufu. His domain was not wealthy enough to finance the work to completion. In order to raise the necessary funds, the burden was passed on to the local citizens, and farmers suffered from heavy land taxation. A harsh and gloomy atmosphere hung over the Shimabara Peninsula.