Shirou Tokisada Amakusa, sometimes called Shirou Amakusa or simply Amakusa, is a recurring boss and playable character in the Samurai Shodown series and the first known agent of the series' major villain, Ambrosia, the Dark God of the Makai.

Amakusa is an alternate portrayal of the historical figure of the same name. The historical Amakusa led a Christian rebellion in the Shimabara region of Japan where the bakufu army crushed his revolt and executed him.

In the series, he is portrayed as an evil sorcerer wielding the Palenke Stone. The portrayal shows hints and views of what the Japanese at the time period perceive Christianity as: an unnatural force of evil and a tool for conquest from outside forces. Though this series' portrayal of him bears similarities with the Amakusa in Makai Tensho, the developers haven't confirmed if he was particularly based on him.

Betrayed by his own men and killed by the bafuku, Amakusa is a mad and vengeful spirit, resurrected by Ambrosia as a being of destruction to put up a new world order. Once he is relieved of the dark god's possession, he reverts to his living persona as a kind and merciful soul of righteous constitution. He is a narcissist by nature, which is what originally lured him to Ambrosia's temptations.

True to the historical Christian Amakusa, he speaks of sin, mercy and salvation, especially in later appearances. However it seems he is still hateful towards the Tokugawas and their allies and finds it difficult, if not impossible, to forgive them.