Upheaval in the Castle and an Imperial Princess

Upheaval in the Castle and an Imperial Princess (帝都動乱、そして帝国の姫) is the fourth episode of the second season of In Another World With My Smartphone anime.

Plot
Touya visits the Regulus Empire for more books for his library café and finds civil war has broken out. Rescuing a soldier about to be executed, Touya learns that the army launched a coup d'état against the empire. After Touya healed the wounded soldier, he heads to the empire's castle and hears a distressed young girl. Using his smartphone, Touya locates and saves her; he also healed the wound near her shoulder. A soldier named Carol then arrives. When Touya explains his background and his use of teleportation magic, Carol begs him to use it to rescue the King, Prince, and Princess to safety, which was his initial plan.

Carol then formally introduces herself, as does the young girl who was Lucia Rea Regulus the third princess of the Regulus Empire. It's then decided to rescue the Emperor and Prince, and they first head to the Emperor's bed chamber. There they find General Bazoar accompanied by his soldiers surrounding the unconscious Emperor on the ground. Touya demands to know Bazoar's motives and claims that the Emperor has become mentally ill and intends to invade Belfast, Mismede, and Refreese.

Using one of his Artifacts, Bazoar summons a demon with excellent resistance to magical attacks, which is also shared with Bazoar. He also wore an Artifact granting him excellent resistance to physical attacks. Seeing that the Emperor is still alive, Touya teleports Zephyrus, Lucia, and Carol away despite Lucia’s brother Prince Romero being nowhere to be found; this shocks Bazoar. Before teleporting himself out of there, Touya casts Slip and Mirage on the two and leaves with a haughty laugh.

Back at Belfast Mansion, Touya's fiancés are briefed about the situation in Regulus. Later, Touya checks on the Emperor, whose condition has stabilized, and Lucia requests Touya to call her Lu for now on. Yumina enters the room, introduces herself to Yu, and, sensing her crush on Touya, invites her to a private conversation.

Meanwhile, Touya informs King Tristwin about the situation in Regulus, who, in turn, announces the Queen is pregnant. If it is a boy, he will inherit the throne instead of Touya, which the King had intended by marrying Touya to Yumina. Later Rosetta reveals that the two artifacts Bazoar has should be from the Storehouse Island.

Late that night, the Emperor awakens. After promising to find Lu's missing brother, Touya uses his memory magic on Lu and locates Romero after using his search function on his smartphone. With the help of his fiancés, Touya defeats the demon's physical resistance by hitting it on the head with his sword, enchanted by Gravity to weigh hundreds of tons. He then defeats Bazoar’s magic resistance by exposing him to a Sludge-slime emitting such a foul stench. Bazoar then faints. Zephyrus reclaims his throne, but Touya cannot celebrate with his fiancés, who are repulsed by the Sludge-slime stench stuck to his clothes.

Characters

 * Wendy
 * Caroline Rillettes
 * Lucia Rea Regulus
 * Touya Mochizuki
 * Rebecca
 * High Rosetta
 * Yumina Ernea Belfast
 * Tristwin Ernes Belfast
 * Prim
 * Linze Silhoueska
 * Reliel Rehm Refreese
 * Kohaku
 * Will
 * Neil Suleiman
 * Elze Silhoueska
 * Zanac Zenfield
 * Zephyrus Roa Regulus
 * Yae Kokonoe
 * Sango and Kokuyou

Differences

 * Unlike the LN, Renne does not find out about her bloodline nor does she know that Carol is her aunt.