This practice has long been in place. This means that potentially there arises a risk of statelessness for all cases where naturalization is about to be approved. Even if the previous country of nationality allows for cancellation of the loss of nationality or for recovery of nationality, statelessness would arise at least temporarily. On the other hand, as in Case 12 (hereinafter the “failed restoration of nationality” type in this section), there can be cases where persons concerned believe that their previous nationality β can be restored or that they still possess country β’s nationality, and at their own will they renounce their current nationality α; but against their expectation they fail to have β’s nationality recovered and fall into statelessness. (2) Possible size of Category F Despite this, it is quite difficult to identify the number of cases where this these sorts of “naturalization failure” or “nationality restoration failure” cases occur. While it is assumed that the majority of “naturalization failure” cases are those who fail to naturalize as Japanese persons, these should not be exhaustive of the category. Even if the focus is put on the cases arising from naturalization as Japanese nationals, it is not possible to identify how many cases of persons who have been “informally approved” for naturalization indeed get rejected at the end, as the statistics relating to the cases that have been “informally approved” is not publicly available. Furthermore, the number cannot be estimated based on the number of cases of rejected naturalizations.191 This is because the number of rejections may not cover all cases of “failed naturalization” as it also happens that applicants are requested by the officials in charge to withdraw their applications upon having their informal naturalization approvals cancelled. Additionally, with regard to the “nationality restoration failure” cases, it is unknown how these cases arise in relation to which cases. It is quite difficult thus to estimate the number of cases falling within this category. 5. Solutions for Category F (1) Prevention First, in order to prevent statelessness from arising out of cases involving “naturalization failure”, it is most crucial to rectify the current practice of requesting naturalization applicants to renounce their current nationality before naturalization is formally approved. 191 As a reference, the number of rejected applications for naturalization was 332 in 2013, 509 in 2014, 603 in 2015, and 607 in 2016; the number of applications for naturalization was 10,119 in 2013, 11,377 in 2014, 12,442 in 2015, and 11,477 in 2016. Ministry of Justice, “Kika Kyoka Shinseishasuu, Kika Kyokasha, Oyobi Kika Fukyokashano Suii [Number of Applications, Grants and Rejections on Naturalization]” (12 May 2017, corrected version), at http://www.moj.go.jp/content/001180510.pdf. 93