Mizuki sat in front of Shoji and adjusted her hair. This time, she had it down, held back from her face by a blue flower pin. Wearing a white blouse paired with a beige wool skirt, she looked more down to earth than he’d remembered.

‘Excuse me for being direct,’ Shoji began. ‘You told me you knew something about Yoko.’

‘Yes, the file is in front of you.’

She gestured to a blue folder on the table, on top of a pile of mathematical journals. A yellow Post-it note with ‘for Shoji Arai’ in neat handwriting was stuck on it. How could he have missed it? He was so tired and disorientated.

‘May I?’ Shoji asked.

‘Please do,’ Mizuki said, reaching for her glass of water. ‘It’s a report done by a private detective I hired after my husband passed away.’

‘Why would you do that?’

She paused. ‘I wanted to do something for you.’

‘Your husband’s family let you investigate?’

‘Nobody knows. I commissioned the detective myself,’ she said. ‘My husband and I had no children, so after he died his family took care of his affairs. I got a decent settlement and was left on my own. No one pays attention to what I do, as long as I keep quiet.’

Shoji opened the file and saw an enlarged close-up photograph of Yoko, alongside her name, age, height, and weight. Underneath the page were various pixellated printouts taken from security cameras. Yoko wore a white sweater and jeans. She carried a huge rucksack as if she were going on a long backpacking trip. He examined the pictures closely. The place looked familiar.

‘Is this Narita airport?’ Shoji asked.

‘That’s right,’ Mizuki said. ‘We’re lucky the airport kept their footage for so long. Security reasons, I suppose.’

‘Uh-huh. Where did she go?’

Mizuki pursed her lips. ‘I’ve no idea.’

‘When were these photographs taken?’

‘The same week my late husband found out what had happened,’ Mizuki said. ‘Four days after the fire.’

Shoji paused. ‘She knew something was going to happen.’

‘She must have got wind of it somehow and hastily packed up.’

‘I don’t understand …’ He stared at the printouts again. No doubt about it, the woman in the picture was Yoko. ‘Who told her?’ Could it be the mysterious man he spoke with on the phone? ‘Why did she leave without telling me? If I hadn’t been out, I could have been burned alive in that building.’

Mizuki bit her lip. ‘I’m not trying to justify the fire, but it wasn’t meant to take any lives. It was a warning. Were you aware that there were zero casualties?’

Shoji nodded, remembering what Uncle Hidetoshi had told him. ‘Kind of.’

‘That’s good. I thought you didn’t know, since you disappeared on the same day. Wise choice. Yoko must have had her reasons to do the same.’