I have read this good manga but I can't remember the title. It starts with the heroine in bed and realized that she got drunk and had a one night stand with a younger co-worker (part-timer). Everyone in the office thinks the part-timer is gloomy or shy because he seldom talks. Eventually they start going out but its a secret to everyone in the office. The young co-worker have black hair.

The last time I read it, the series is still on-going...

Sorry that's all I remember. it would be good if anyone can help. Thanks!

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I will try to mirror your worth...

I already found the title. Its kyou wa kaisha yasumimasu.

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I will try to mirror your worth...