Kirk here. The numbers of visits of foreign tourists to Kumamoto City have been rising in recent years. The blue bars represent numbers of foreign tourists; yellow bars show numbers of such tourists who spent the night. I'm not quite sure how the numbers are calculated, especially for people who don't spend the night (no border check to see if a foreigner in Oita drove in to Kumamoto to look around, for example) but I don't doubt the overall trend.
Note: Y-axis values are in units of 万 (10,000). So, in 2025 there were approximately 180万 or 1.8 million foreign visitors.