Igniting Winter for Her- Only the Sister's Guardian Magus

After failing a magic trial at Flame Academy, neglected foster‑son Arthur accidentally unleashes hidden immense power. When his beloved non‑blood sister Allara is forced into a deadly political marriage to cruel Caelum from Thunderhead Academy, Arthur tries to rescue her but gets defeated and falls off a cliff. Grand Archmage Elric saves him, revealing Arthur possesses extraordinary dormant magic and takes him as disciple. While Arthur trains hard, Allara suffers brutal abuse in Thunderhead. At the royal tournament arena, Arthur reappears, defeats enemies and kills Caelum, sparking kingdom‑wide manhunt. In fierce battles, Arthur summons a frost‑dragon phantom. The truth unfolds: he is the kingdom’s long‑lost true prince, whose throne was seized by the current usurper king. Standing outside the capital gate, Arthur floats mid‑air with his frost‑dragon, confronting the whole royal force to claim his birthright and protect Allara.