The Fukushima nuclear power plant accident that occurred in March 2011 caused widespread environmental pollution and severe socio-economic damage. Since December 2012, collective lawsuits have been filed by the victims of the disaster all over the country. The number of plaintiffs exceeded 12,000 with about 30 lawsuits. This study first presents an overview of the current status and challenges pertaining to the collective complaints filed with the Nuclear Damage Compensation Dispute Resolution Center (Alternative Dispute Resolution (ADR) Center). The ADR Center is a government agency intended for, as the name suggests, alternative resolution of disputes. As an example of a collective complaint, we introduce the case of Kawauchi Village. Regarding collective complaints, due to TEPCO's rejection of settlement proposals, the number of cases in which settlement mediation procedure is terminated is increasing. As collective complaints are in a very difficult phase, some victims, whose mediation procedures were terminated, have proceeded to collective lawsuits. Three high court rulings pertaining to the collective lawsuits were made in March and September 2020. Moreover, 17 district court rulings were made between March 2017 and August 2020. It should be noted that many court rulings independently determine damages without adhering to the guidelines of the Dispute Reconciliation Committee for Nuclear Damage Compensation and TEPCO's compensation criteria. However, the court rulings vary considerably, and the damages cannot significantly exceed the amount specified in the guidelines/criteria. Compensation for the "loss of hometown" is being approved in court for the designated evacuation zones, but the compensation amounts are lower than those sought by plaintiffs. If a court rules that damages not covered in the guidelines are to be paid, the guidelines should be revised accordingly. The Japanese government was not a defendant in these two trials. On September 30, 2020, the Sendai High Court ruling was made in the "Nariwai［livelihoods］Trial," which had the largest number of plaintiffs. Among these collective lawsuits, it was the first high court ruling that recognized the government's liability. The high court ruling followed that made by a district court that also recognized the government's liability. Furthermore, the issues pertaining to TEPCO's disaster prevention measures were strictly highlighted and were treated as important factors to be considered upon the estimation of damages. The ruling approved compensation for the "loss of hometown" in the evacuation zones, which was denied in the first instance, and awarded compensation of a comparable level to that awarded by the Sendai High Court ruling in March 2020. The damages awarded significantly exceeded the amount approved in the first instance. Damages that are awarded to areas outside of the evacuation zones remain low, but the compensation was extended to areas that have not been approved by the district court, including the Aizu region and areas outside the Fukushima prefecture. Based on the above, it can be concluded that the discussion on damages has advanced for the plaintiffs and lawyers since the first-instance ruling.