Academy City SNS Rondo Net

Academy City SNS Rondo Net (学園都市SNS ロンドネット), or Rondo Net (ロンドネット) for short, is a social networking site which appears in Toaru Majutsu to Kagaku no Ensemble.

Principles
Aside from allowing registered users to communicate with one another, Rondo Net can also be used for purchases and acquiring special coupons.

As part of his plan, Pantagruel incorporates a spell into Rondo Net. Following a system update, Rondo Net's user agreement includes a functional magic contract, which incorporates those that accept the agreement into the spell. Upon activation, the spell creates a virtual Academy City on Rondo Net, synchronized with the real one, with anything happening to the avatars in the virtual city occurring to their real-life counterparts. Various effects are also be produced by altering object parameters. Sigils are incorporated into the spell's construction.

Silver Star Miracle
The Silver Star Miracle (シルバースターの奇跡) is an event that takes place on Rondo Net, ending with the appearance of a shooting star. The true purpose of the event is to allow Pantagruel to summon Aleister Crowley be he dead or alive.

Background
Rondo Net was devised and launched in Academy City at some point prior to the opening of Endymion. At some other point, Pantagruel made plans to make use of Rondo Net to implement his plan.

Toaru Majutsu to Kagaku no Ensemble
A few days before the opening of Endymion, Rondo Net was becoming popular among Academy City's students and the number of users had grown explosively. Around the time of the Venus Probe Contest, a related event called the Venus Probe Project Race was held on Rondo Net. Kamijou Touma attempted to sign up for this event but was unable to do so, encountering an error.

Pantagruel, using the actions of Gate of the Gods Come from the Heavens as a cover, infiltrated Academy City and took over the company responsible for Rondo Net. When Rondo Net went down for maintenance that night, Pantagruel incorporated a magic contract into the new user agreement which would integrate anyone who agreed to it into his spell. He covered his tracks by disposing of the company's data and casting the employees into confusion with magic.

While investigating the "uninvited guest", Tsuchimikado Motoharu discovered a weak magic being emitted from phones connected to Rondo Net and realized what had been added to the user agreement the previous night. Investigating the company behind Rondo Net, he and Kanzaki Kaori discovered that it had been abandoned, with all data physically deleted then magically destroyed to make certain, and just a star mark left behind. They visited a member of the company in hospital but due to magic cast on him, they could only get a few words out of him. They also received a notice that various key Academy City utilities were being incorporated into Rondo Net, meaning everyone in the city would be affected by the spell.

As their request to shut off the central system to stop the plot was denied, Kanzaki attempted a ceremony using her qualities as a Saint to disrupt the balance of the Rondo Net spell. However Pantagruel intervened, putting Tsuchimikado at risk and forcing Kanzaki to save him, giving him enough time to implement his plan, creating a virtual Academy City on Rondo Net with everything in the real city synchronized to their virtual equivalents. He then removed Kanzaki's parameters to prevent her from interfering again.

Pursued by Tsuchimikado, Pantagruel appeared before Kamijou Touma, Ureapaddy Exica and Sozty Exica, after their battle. After countering Ureapaddy's attack by threating Sozty, Pantagruel then realized that Kamijou Touma was the only person unaffected by his spell, due to the Imagine Breaker negating the spell from his phone, causing a data rollback in the process. Touma attempted to fight him but he wasn't able to match Pantagruel's Saint-class parameters. Pantagruel tried to summon Aleister Crowley using the Silver Star Miracle but failed as he didn't take the Misaka Network into account. Before he could try again, Ureapaddy Exica made use of her Brahma Astra to create an opposing spell which destroyed it, causing Pantagruel to lose his increased parameters. After being punched by Touma, Pantagruel was able to regain some functionality from the Rondo Net spell in order to escape.

After Pantagruel escaped and planned to start again, Aleister Crowley took control of the Rondo Net spell and used it to 'roll back' the city to an undamaged state before using it to erase Pantagruel from existence. It isn't known what exactly became of Rondo Net after that.