💡 Detailed Explanation
Translation: I want to go to Japan next year.
- Grammatical point: Expressing desire '〜たい' (want to do) and polite endings.
- Explanation: The suffix '〜たい' (tai) behaves grammatically just like an i-adjective (い形容詞). To make it polite, we simply add 'です' (desu). It cannot be followed by 'ます' (which only attaches directly to verb stems, e.g. 行きます).
- Tense Check: 'らいねん' (next year) refers to a future event, so past-tense endings 'でした' or 'ました' are incorrect.