日本首相高市早苗指出，若台湾遭受攻击且中国为阻止美军介入而对美军发动打击，日本将面临“生存受到威胁”的局面，此概念源自2015年安全立法，适用于日本未遭直接攻击但其存立与国民生命受到明显危险的情形。她强调仅以民船阻碍通行不足以构成此级别，但若为战时封锁并伴随无人机与其他军事动态，则可能达到门槛。日本国会质询聚焦中国为实现对台湾“完全控制”可能采取的措施，以及此类危机中日本是否必须进行最坏情况准备。

美国过去质疑自卫队在日本未受攻击的情况下能否与美军共同作战，2015年立法赋予自卫队在“生存受到威胁”情形下实施有限集体自卫的能力。台湾距离日本与那国岛仅110公里，使美军在日基地在台湾危机中可能成为攻击目标。历届政府内部探讨自卫队在台湾有事中的角色，但在公开场合保持模糊。岸田文雄过去也以“综合判断”回应类似问题，显示政府长期避免明确界定触发条件。

在最新的国会审议中，高市的具体化表述引发在野党的批评，认为“不应轻率谈论武力行使”。防卫相小泉进次郎警告公开具体情境等同“亮出底牌”，将使对手更易规划攻击。他强调必须保持政策反应的弹性，与要求明确列举情境的质询方式存在根本差异。

Japan’s Prime Minister Sanae Takaichi stated that if Taiwan were attacked and China struck U.S. forces attempting to assist Taiwan, Japan would face a “survival-threatening situation,” a concept from the 2015 security legislation applying when Japan is not directly attacked but its existence and citizens’ lives are clearly endangered. She noted that civilian shipping disruptions alone would not meet the threshold, but a wartime blockade with drones and other developments could. Diet questioning centered on measures China might use to bring Taiwan fully under Beijing’s control and whether Japan must prepare for a worst-case scenario.

The United States has previously questioned whether the SDF could operate jointly with U.S. forces if Japan were not attacked; the 2015 law granted the SDF limited collective self-defense capability under survival-threatening conditions. Taiwan lies only 110 kilometers from Yonaguni, making U.S. bases in Japan potential targets in a Taiwan crisis. Earlier governments examined SDF roles privately but avoided public specificity. Former Prime Minister Fumio Kishida also relied on “comprehensive judgment,” continuing long-standing ambiguity.

During the latest Diet session, Takaichi’s specificity prompted opposition criticism that force should not be discussed lightly. Defense Minister Shinjiro Koizumi warned that presenting concrete scenarios would “reveal Japan’s hand,” easing an adversary’s planning. He asserted the need for flexible responses, rejecting approaches demanding detailed predefined cases.