Polite to Colleague
Workplace · Lunch
You
お昼ご一緒にいかがですか？
おひるごいっしょにいかがですか？
Would you like to have lunch together?
Romaji: Ohiru go-issho ni ikaga desu ka? / Reply Romaji: Ii desu ne! Doko e ikimasu ka?
Reply
いいですね！どこへ行きますか？
いいですね！どこへいきますか？
That sounds great! Where shall we go?
Gesture & etiquette
A relaxed, friendly expression and light tone; approach at a natural moment (not mid-task); if they hesitate, 'お時間があれば、ぜひ' (whenever you have time, please) removes any pressure.
Sharing lunch is one of the easiest ways to build informal connection in a Japanese workplace. If inviting a superior, add 'よろしければ' (if that's alright with you) at the start to make it appropriately deferential. Refusals are usually polite ('今日はちょっと...', today is a bit...); don't push — they will reciprocate when ready.